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SLP Power-Flo Cat-Back Exhaust (99-04 GT, Mach 1)

Market Price $529.95 You Save 4% ($21.00)
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  • Item 23012
  • MPN# M31004

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Features & Details

  • Classic Muscle Car Sound
  • "Power-Flo" Mufflers Included
  • Versatile Modular Design
  • 2.5" 409 Stainless Steel Tubing
  • 3.5" Polished Stainless Steel Tips
  • Fits 1999-2004 GT, Bullitt and Mach 1 Mustangs
Classic Muscle Car Power And Sound. This SLP system includes SLP's Power Flow "straight-through" mufflers that are designed to provide an optimal balance of exhaust flow and sound level to free up more horsepower and to produce a classic muscle car rumble.

Modular Design. SLP's unique modular design allows you to quickly and easily switch out the mufflers or resonators to suit your driving needs. Along with the included Power Flow Mufflers, the Power Flow catback system is compatible with all SLP mufflers and resonators including the bullet-type Loud Mouth II and the shotgun-style Loudmouth Resonators.

Superior SLP Construction. This SLP Cat-Back system is made from mandrel bent 2.5" 409 stainless steel tubing for its excellent non-restrictive flow characteristics and long life. The system ends with brightly polished 304 stainless steel 3.5" tips, that are electro-marked with the distinctive SLP logo, giving a great finishing touch and a show quality look.

Application. Designed to be a direct bolt on, this SLP Power Flow catback will bolt straight up to the factory Mid-Pipe without any extra modifications required on the 1999-2004 GT, 2001 Bullitt, or 2003-2004 Mach 1 Mustang to give it a classic throaty rumble.

Fitment: 1999 2000 2001 2002 2003 2004 Details

What's in the Box
Hardware included:
  • (4) band clamps
Installation Info
About The Brand

About SLP


Tech Specs
Cat-Back Exhaust Specifications
Piping Material: 409 Stainless Steel Tip Material : Polished 304 Stainless Steel
Piping Size: 2.5" Tip Size: 3.5"
Muffler Type: Chambered Fitment: 1999-2004 GT / Mach 1 / Bullitt Mustangs
Will it fit my Mustang?
  • Bullitt - 01
  • Mach 1 - 03, 04
  • GT - 99, 00, 01, 02, 03, 04

Fits GT, Mach 1, and Bullitt

Most Helpful Reviews

SLP Powerflo

Perfect exhaust system for those that do not want excessive noise at cruising speeds. Nice deep tone. Kit fit perfectly. Some pipe connections were fairly loose and clamps needed to be tightened up a lot, ...

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Helpful (4)

Slp rocks!

Sounds great! Fits great! Not much more to say.

Helpful (2)

Overall Rating 4.8 out of 5 stars
Read All 17 Reviews

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Customer Reviews (17) Write a Review

Overall Rating 4.8

out of 5 stars

Installation Time:Afternoon

  • Loudness / Volume 4.181818 4.2
  • Exhaust Note 4.727273 4.7
  • Fit & Finish 4.818182 4.8
  • Bang For Your Buck 4.636364 4.6

  • 5/5

    December 09, 2009

    SLP Powerflo

    Perfect exhaust system for those that do not want excessive noise at cruising speeds. Nice deep tone. Kit fit perfectly. Some pipe connections were fairly loose and clamps needed to be tightened up a lot, other than that it was an easy installation. Tips look better than stock.


    Helpful (4)

  • 4/5

    Installation Time: Shop Install

    January 01, 2012

    SLP Power-"Flo"

    SLP makes superior exhaust products and this cat back is a perfect example of what they do best. Install took roughly an hour without any issues. Don't fret when you get excited about having it installed and then hop in your pony, rev it up and notice something not that loud. From what I could tell they are glass packs and will definitely get louder with age. I've had mine for about a month now and it is without a doubt a deeper throatier tone than it was right after the install. Used to have Flowmaster 40s that had an annoying drone around 2k rpm, not with these though. This exhaust is the reason I gun it any chance I get.


    Year: 2002 Submodel: GT Harrisburg PA

    Helpful (2)

  • 5/5

    March 18, 2010

    Slp rocks!

    Sounds great! Fits great! Not much more to say.

    Aaron Ramsey

    Helpful (2)

  • 5/5

    Installation Time: Afternoon

    June 29, 2014

    great fit and sound

    Great fit. Sounds great not to extremely loud. Also has bbk long tube headers and bbk off road H pipe.


    Year: 2004 Submodel: GT

    Helpful (1)

  • 5/5

    January 11, 2009


    Exactly what I was looking for! If you have headers and mid pipe this exhaust is perfect. It gives your pony that healthy rumble, while not being over the top loud at the same time. I had the slp lm1s and they just made noise. With the power-flo i actually picked up some bottom end! Thanks American Muscle for a fast delivery and a great product!


    Helpful (1)

  • 5/5

    September 16, 2009


    Perfect! Loudmouths are so obnoxious and sound like ricer exhaust. The powerflo has all the rumble you need.


    Helpful (4)

  • 5/5

    Installation Time: Afternoon

    April 25, 2013

    Pops is Happy!

    Exhaust sound is a personal thing and I spent hours looking for the "right" one. I didn't want to wake up the neighborhood - just something that was deeper and throatier than stock. I did the install alone with jack stands (four for safety) and it took about three hours. I had absolutely no problems and no adjustments were needed. When I finished, I took it out and will describe the ride as aggressive but not over the top. Make a note that the system will scream when you get on it. For the outside experience, I had a friend drive with me following so I could hear what everyone else does. The sound is deep and subtle simultaneously . It is one of those "what is this guy running?" sounds. I think I made the perfect choice and am very impressed with the SLP's quality and fit. p.s. The directions don't specifically say it, but drop the pipes behind the "H" section AND the two brackets (4 bolts) behind the mufflers BEFORE you make your cuts. If you do that first, the cuts are easier and you won't have to worry about the brake lines. Make sure you are out of the way when you cut through. Mufflers and pipes are heavier than you think!


    Year: 2003 Submodel: Mach 1 Highland Village, TX, USA

    Helpful (0)

  • 4/5

    Installation Time: Afternoon

    February 26, 2012

    not loud

    product fits well and functions well and installation was easy. however, product is not as loud as expected and not nearly as loud as the video on the website. if you are looking for a louder than moderate exhaust, try the SLP loud mouth.


    Year: 2004 Submodel: GT Chicago, IL

    Helpful (0)

    • Response from AmericanMuscle

      Sorry to hear that this SLP kit didn't perform exactly how you expected it to. A chambered set up like these Power-Flo mufflers will generally be a good deal quieter than a resonator or straight through set up like the Loud Mouths. If you want the car even louder, I'd highly suggest swapping in an aftermarket X-Pipe like this one from Pypes: It will increase the volume of your exhaust significantly, and help you pick up some power too. If you're still not happy with the sound of the exhaust, give us a call and we'll do our best to hook you up with something that you're happy with!

      Rob , Product Content

  • 5/5

    July 21, 2011

    SLP Power-Flo Catback

    I received my SLP system only a couple days after my order was placed and had them installed the next day. It gives the car a deep growl without any drone at speed and the tips looks great out the back of the car.


    Year: 2003 Submodel: GT

    Helpful (0)

  • 5/5

    June 17, 2008


    Sounds great and looks cool


    Helpful (0)

  • 5/5

    Installation Time: Afternoon

    December 09, 2016

    Great system

    If you want a good sound that's not too loud then this is the one for you. Fits perfect. Great price.


    Year: 2003 Submodel: Mach 1

    Helpful (0)

  • 5/5

    Installation Time: Afternoon

    March 02, 2014

    Nice fitment. Nice hardware included in kit.

    I recently installed this kit with my new BBK high flow cat x-pipe. This exhaust system is very easy to install. All pipes are label for ease of install. Clamps included in kit are higher quality band style exhaust clamps. Mufflers and tips are very high quality. Exhaust produces a great "tuned" sound. Exhaust does produce slight drone from 1900-2300 rpms. Drone is note over bearing though. Very happy with this exhaust. Great bang for buck!


    Year: 2003 Submodel: Mach 1 Hermitage, Nashville, TN 37076, USA

    Helpful (0)

  • 5/5

    Installation Time: Afternoon

    September 17, 2013

    perfect sound, fit, and finish

    For me this is the perfect loudness and sound. Louder than stock, but quieter than the loud mouth 2 that I had before it. This is a straight through muffler also, no chambers. A cross section can be seen on SLP's website.


    Year: 2004 Submodel: Mach 1 nj

    Helpful (0)

  • 4/5

    Installation Time: Afternoon

    September 13, 2013

    Great budget exhaust

    I needed a new catback for my Mustang Cobra when I did a SRA swap. I was looking for reasonably priced systems when I came across the SLP Powerflo catback. I had the LM1 on my old GT and I liked it the but after 3+ years of the very loud LM1's it started to get to be too loud. Sometimes I like the loudness of the LM1's and other times I didn't like it. The Powerflo system was basically everything I was looking for. With the straight through design of the Powerflo, it's loud when you want it but somewhat docile when at idle, low RPMs, or at cruising speeds. It's not quiet, just not ridiculously loud like the LM1's. All in all it fits well once you get everything aligned, it sounds great, and it screams at WOT. I'd recommend this system and any SLP system to anyone looking for a good bang for the buck catback system.


    Year: 2003 Submodel: Cobra Maryland

    Helpful (0)

  • 5/5

    Installation Time: Afternoon

    August 08, 2012

    Excellent Product

    First and foremost, fit and finish is awesome. I gave it 5 stars for bang for your buck because of the fit and finish, otherwise it would have gotten 4 stars. Installation was very easy, with removal of the old parts taking the longest time of the approximate 4 hours total R&R. My only issue is with loudness because the exhaust does not really sound as loud as the video on this website. I have no comparison to stock, but the Power Flo mufflers are substantially quieter than the Flowmaster's I replaced, VERY quiet in comparison. Gone is the dreaded "drone" of the Flowmaster's at 2000 rpm as noted by other reviewers. Lastly, I will say that the quietness is starting to grow on me, but these mufflers do tend to "bark" quite a bit under "spirited" driving.


    Year: 2001 Submodel: GT

    Helpful (0)

  • 5/5

    Installation Time: Afternoon

    January 14, 2012

    Slp is a quality product

    I love the way this exhaust looks and it sounds sooooo much healthier than stock. It is a deeper growl. Not much louder than stock at first and you can cruise on the freeway with it. But when you punch it you can really hear your pony roar. From what I've been told they take about six months to break them in, so over the next six months they will slowly get louder. I will leave another comment on here in a few months and let you guys know how it sounds and how much louder it gets. Slp makes quality products. IMO these are better sounding and quality than flowmasters.


    Year: 2001 Submodel: GT Stockton, CA

    Helpful (0)

  • 5/5

    Installation Time: Afternoon

    October 24, 2011

    Great fit, awesome sound.

    These shipped in 4 days, got them off the truck and straight to the shop.. install was easy, they fit great, and sound way better than the flowmasters I had on there. I recommend these, definately.


    Year: 2003 Submodel: GT

    Helpful (0)

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