Which Exhaust Set-up Provides the Most HP for an ’06 GT?

Ford Mustang Q&A

Karl A asked: “I just purchased a 2006 GT convertible. I really want to put a lot of time and money into my new car, not only to make it look good, but powerful too. The first thing I want to do is upgrade my exhaust. I’d like a strong old school muscle car rumble and growl but I don’t exactly know where to start. I have been told to get Flowmaster axel back mufflers with cross pipes. I have been told H pipes are good, and many other options. My goal would be for extra power, and of course, a loud, muscular sound. I would appreciate any advice here. I want to put work into my new car and do it right!”

An aftermarket exhaust is a great place to start when modding any car. A complete system can add an extra 40 hp at the rear wheels with a tune. Our tech article on understanding exhaust systems is a must-read for any first-time modder. Before I get into the nitty-gritty of exhaust systems, here are some important points everyone should know about aftermarket exhausts:

  1. Purchase your headers and mid-pipe from the same manufacturer – some manufacturers sell products that only bolt up to their own, or OEM, exhaust components.
  2. Long tube headers sometimes require oxygen sensor extensions, but always require a new mid-pipe (shorty mid-pipe).
  3. If you choose to run an exhaust with no catalytic converters you will need to re-tune the computer to get rid of the check engine light.

IMPORTANT – Although some high-flow catalytic converters will pass state emissions testing, it is still illegal (under federal law) to run anything other than a catalyst that meets OEM specifications. You should always be aware of the state and federal emissions laws.


A lot of customers ask me about the difference between short tube and long tube headers. I think much of this confusion stems from the fact that the power gains are relative to RPM range. Long tube headers give more consistent power, not necessarily more power. This means that the long tube headers will give power from mid-low RPMs through mid-high RPMs, whereas the power increase from shorty headers is limited to mid-range RPMs.

SLP Mustang Headers

Considering that Karl wants the most HP from his exhaust, my recommendation would be a set of ceramic-coated SLP long-tube headers. The ceramic coating is an awesome insulator, it conducts almost no heat and yes, that is a good thing. Hot gas moves faster than cool gas, so keeping the exhaust gases hot moves them out of the engine bay faster, improving efficiency.


Mid-pipes are another subject I get a lot of questions on. What’s the difference between an X-pipe and an H-pipe anyway? First of all, a mid-pipe with a crossover is essential, it evens out exhaust pulses and the intermingling of the exhaust gasses equalizes backpressure between the two banks of the engine.

An X-pipe provides the path of least resistance, so to speak. Keeping the exhaust gases moving parallel to the walls of the tubing prevents “tumbling” and maximizes horsepower and efficiency by maintaining speed. While you won’t see as many horses with an h-pipe, they are touted for their low-end torque. H-pipes also encourage the “tumbling” effect of the exhaust gases, making them several decibels louder than an x-pipe. My recommendation for Karl here would be a shorty SLP catted x-pipe to match his headers.Magnaflow Mustang Exhaust


This is the biggest factor in the actual sound. The headers and mid-pipe will affect the sound of your exhaust to a point, but nothing affects the sound of your ‘Stang more than the mufflers. Generally, the freer-flowing the exhaust, the more power you get. Even though Karl wants to boost horsepower, I would still recommend a system with chambered mufflers like a Magnaflow stainless cat-back system. This chambered-muffler system will give Karl the muscle car rumble he wants without that maddening drone at highway speeds.

  • kyle kurt

    similar question, but u have a 95 v6, any thing you can say to help me out

    • http://www.americanmuscle.com/ Heather

      While we don’t have any long tube headers available for the V6s, these shorty headers would definitely be an improvement over stock:
      It can be tough to find exhaust parts for the 94-95 V6s, but this dual exhaust conversion kit allows you to use a GT cat-back system and greatly improve flow:

    • John

      Can i put the recommended x-pipe on my 2005 mustang gt without putting on the longtube headers for now?… those headers are quite expensive and was wondering if i can put on the x-pipe without the headers? Thanks

      • http://www.americanmuscle.com/ Heather

        You will not be able to install a shorty mid-pipe without long-tube headers, they won’t work with shorty or stock headers. However, you could get a standard-length x- or h-pipe that would work with shorty/stock headers.

      • John

        Thanks Heather… i was looking at both, but then i realized that the headers do not fit convertibles, which i have. What gives? and what would be the next best ones (that fit convertibles)?

        • http://www.americanmuscle.com/ Heather

          Finding LTs that fit convertibles is difficult – Check out my response to Phil Guza’s question a little further down, that may help you out :)

    • rob

      i had a 99 v6 with the pypes o/r x pipe with slp lm1s. i noticed alot of power gain for a v6

      • David

        were did you get those i was thinking of getting long tube headers for my 04 v6 but any advice would be very appreciated. which ones are the best for my 6

        • http://www.americanmuscle.com/ Heather

          Mac and Pacesetter both have long tubes available but the quality/fit of Mac’s product is questionable and the Pacesetter product does not come with flanges – they have to be welded on. The other option is having a custom set made, which can be very expensive. I am looking into making LTs for the V6s available though, so stay tuned! :)

          • Edward R

            is the fit on the mac product really THAT bad????????

  • http://None Erik

    For any V6 I would always recommend a true dual exhaust with a h-pipe or x-pipe. Not those quick fix dual muffler setups that bolt the the stock y-pipe exhaust. H-pipes give you that low end rumble and more torque. X-pipes give you a high pitch import exotic sound but more horsepower at top end but you will give up midrange torque on naturally aspirated cars. I know 2 brands that carry a true dual conversion kit for the 94-98 stangs one is pacesetter and I think the other is dynomax or mac (but not 100% sure) they usually run $70-$90 dollars but require the stock y-pipe exhaust to be cut and cannot be returned to stock. Honestly I do not recommend the chambered mufflers because the drone will drive you crazy (examples flowmaster, mac, cherry bomb, jba) if your car is a daily driver. I always recommend borla, magnaflow, or dynomax because they sound good and flow better than any chambered muffler. If you decide to keep you v6 a long time try to shoot for a stainless system or at least the mufflers.

    For 05+ GT drivers the factory stock mufflers will handle up to 500hp. They are also used on the GT500. On the dyno we removed the stock mufflers on the GT500 and left the straight pipes & only gained 4 hp and lost alot of torque. It is up to you to pay hundreds of dollars for a just a deeper or louder sound. Only the Magnapaks, borla stingers, and corsas (straight flow design) gain only 3hp over stock axleback at 5500rpm and lost a little torque on a 05GT. But they are each about 10lbs lighter that the stock mufflers. Hope this helps, remember I am not a politician or a salesman.

    • http://www.americanmuscle.com/ Heather

      Good info! I have chambered mufflers on my V6 daily driver and it doesn’t drone at all – I think it depends on what brand muffler you have, as well as how the rest of the exhaust is set up. Since you don’t recommend chambered mufflers, would you recommend a resonator or glass-pack style muffler?

      • 00R

        On a v6 a glasspack/resonator will make the exhaust note tinny as well as above 3000rpms it will sound like a 4 cylinder because of the rasp.

        The best way to eliminate drone as well as rasp is to add aforementioned resonators upstream of the muffler of choice. It will eliminate rasp and drone 100% and leave a nice, clean, and mellow exhaust note. If you want to get away from the deep rumble and enhance the uniqueness of the v6 motor, an x-pipe, resonators, and magnaflow mufflers will create a sound that is comparable to Nissan’s VQ motor (used in the 350z / G35) and can be further enhanced with longtubes.

        Heather for prez!

  • Phil Guza

    Referencing Karl A’s ’06 GT & Kyle’s V-6
    I am surprised to see you reccomend a brand by name when you sell many but thanks b-4 I spend money in the wrong spot. I own a ’07 GT conver’t [lowered] w/Eibach’s Pro-Line series (springs, shocks, struts, front & rear anti-sway bars) for a drop of not more than 1.3″F & 1.6″R) & thought all long tube headers were out for me since the drop (clearance)…true or false 1st please & 2nd, would SLP still be for me if False? If not, who please?
    Another note, you stated in Karl’s V-6 blog that while x pipes give more hores power they also cause the unforgivable import tuner sound (which I loathe) so if I’m mainly after more mid-range H.P & Tq & 70 Chevelle Big Block sound, do I just give up or is there a remedy?
    Since the drop the car is way more “useable” & believe it or not more comfortable & “fun” so says my wife who is the money boss & critic so please advise as to my need for useable/reliable dropped convertible power & speed…I still like to thrash more than straight line if that helps or makes a difference! Afterall, it’s a Mustang which by birth is not an intended “drag-car”…that was why FORD made the Galaxie 500

    • http://www.americanmuscle.com/ Heather

      The fact that your car is a convertible is actually more of an issue than the lowered suspension. SLP long tubes will definitely not clear, but the BBK LTs (item number 56038) would be a great choice for your application. Remember that you will need to use a BBK mid-pipe as well!
      An x-pipe doesn’t necessarily cause the dreaded “import tuner sound”, but if your definitely out for the big-block sound I would recommend an h-pipe.
      If you want to improve handling you might want to invest in some sub-frame connectors and a set of rear end gears.

  • 00R

    Also for an 05+ v6, if you’re on a tight budget find a gt owner that is looking to dump his stock mufflers, they are much less restrictive than the v6’s, they produce a nice mellow tone and increase power as much as any other aftermarket muffler on a N/A motor.

    • 00R

      Oh and heather for prez!

  • Karl Augustus

    Hi this is Karl Augustus the guy who actually asked this question on the Mustang Q&A. Heather I just wanted to thank you for your advice and knowledge. Im actually looking to purchase my complete exhaust system next week which will be comprised of all parts you recommended! Again I can’t express enough my gratitude!

    Karl Augustus

    • http://www.americanmuscle.com/ Heather

      That’s great! I’m so glad I was able to help! :) I’m sure you’ll love the results you get with your new exhaust.

  • steven

    hey in reference to the v6 thing, i had a 00 v6 making 210hp/238tq to the wheels and i had a catless true dual (no crossover because its not needed on the v6) bbk shorty headers, and super 40 flowmasters, and from idle to about 2800 rpm it sounded like a gt, and the rasp did occur from bout 2900-3500 and from there it sounded like a dang stock car at daytona. warning there is a loud drone at highway speeds and if you dont like the drone do not get flowmasters but if you want a nice meaty tone get them. i did not like the magnaflows because it made them sound like the nissan vq. borla did sound alright in my opinion the only two to consider were bassani or flowmaster (40’s delta 40’s super 40s etc.) i always had compliments, and with a tune and some work you can get great numbers outta that 3.8 (split port). i did however convert to a v8 so now im back on the search and decided to use the cherry bomb extreme. it is all what you like. i recommend going to http://www.mustangexhaust.com and listen and find one you prefer. i hope this helps



  • David

    whats best for a 04 v6? i got flow super 44s i like those but i know there is better i got true duals

  • Rick

    I have a question about headers. I own a ’08 mustang gt convertible and I was wondering if the american racing lt and shorty x would fit?

    • Dean

      I have an 08 GT convert that I put BBK shortys, SLP X pipe with cats and Flowmasters on. The install on the shortys is on Mustang magazine’s website. Took 8 hours. The rest bolt right up to the shortys. No clearance problems. You can find my review and that website for the intall on the BBK shorty page on AM

  • Gary

    Thanks for the recommendations! I have an 02 GT that I bought used of a used car lot. I recently had the car up in the air and noticed that the mufflers on it were Magnaflow. Did these come stock on the 02 GTs? I would like to make my car sound meaner without taking a big hit to the wallet and just want to swap out the mufflers. WOuld you recommend the SLP LM!’s or the Flowmaster Delta 44s?

  • Tyler

    I want to do a dual exhaust system for my 2000 V6. I was going to do the V6 adapter H pipe with a SLP Powerflo system. Then it came across to me that i could do a true dual… What would be the difference in sound, what would be the power difference and how much would it cost to just do true dual? Im going to take it to a shop.

  • http://www.solidhex.com patrick

    What about for a 2010 GT :)

  • Juan

    hello I have a 98 4.6 gt mac Lts, mac catted h pipe and the magnapacks it doesn’t sound too bad but im looking for a more aggresive sound what would you recommend. i was thinking about swapping the mufflers to Slp would that do it thanks??

  • Edward R

    i have an 08 gt n just ordered a full mac exhaust…why is mac a questionable exhaust? i know the quality aint too good but why else are they a bad choice?

  • NDwhitehorse

    good discussion! I have a 2007 shelby GT/SC with a factory paxton supercharger…it came with Ford Racing Parts mufflers and x pipe, which are a bit throatier than the stock GT exhaust…but I would like a bit more bite in the sound without too loud of a drone at speed…of course more power would help (475hp just isn’t enough after you get used to it!)…a previous post made it sound like just swapping mufflers won’t do anything more for power tho. Anybody compare the FRP mufflers to something a bit more aggressive, without getting a loudmouth banshee sound?

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