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

16 Reviews
Our Price


  • Item #23012
  • MPN #M31004
  • Market Price $583.99
  • You Save 11% ($63.00)
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Customer Photos
  • 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 Catback 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.

Mustang Fitment: 1999 2000 2001 2002 2003 2004 Details

What's in the Box
Hardware included:
  • (4) band clamps
Installation Info
Tech Specs
Catback 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
  • Bullitt - 01
  • Mach 1 - 03, 04
  • GT - 99, 00, 01, 02, 03, 04

Fits GT, Mach 1, and Bullitt

Most Helpful Reviews View All

Overall Rating 4.8/5 Write a Review
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) (1)

Slp rocks!

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

Helpful (2) (0)

Customer Photos (4) View All

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Reviews (16) Write a Review

  • 5 Stars .81 81%
  • 4 Stars .19 19%
  • 3 Stars 0 0%
  • 2 Stars 0 0%
  • 1 Stars 0 0%

out of 5 stars

16 Customers Recommend this Product

Installation Time:Afternoon

  • Loudness / Volume: 4.1 4.1/5
  • Exhaust Note: 4.7 4.7/5
  • Fit & Finish: 4.8 4.8/5
  • Bang For Your Buck: 4.6 4.6/5
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  • 5/5

    SLP Powerflo

    December 09, 2009

    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) (1)

  • 5/5

    Slp rocks!

    March 18, 2010

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

    Aaron Ramsey

    Helpful (2) (0)

  • 4/5

    SLP Power-"Flo"

    January 01, 2012

    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.

    Top 1000 Contributor


    Year: 2002 Model: GT Driving Style: Daily Driver 'Stangs I have owned: 1 Harrisburg PA

    Helpful (1) (0)

  • 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) (0)

  • 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) (4)

  • 5/5

    Pops is Happy!

    April 25, 2013

    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 Model: Mach 1 Driving Style: Street / Strip 'Stangs I have owned: 1 Highland Village, TX, USA

    Helpful (0) (1)

  • 4/5

    not loud

    February 26, 2012

    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.

    Top 500 Contributor


    Year: 2004 Model: GT Driving Style: Show 'Stangs I have owned: 1 Chicago, IL

    Helpful (0) (1)

    • 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:

      <a href=""></a>

      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

    SLP Power-Flo Catback

    July 21, 2011

    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 Model: GT

    Helpful (0) (1)

  • 5/5


    June 17, 2008

    Sounds great and looks cool


    Helpful (0) (1)

  • 5/5

    great fit and sound

    June 29, 2014

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


    Year: 2004 Model: GT Driving Style: Street / Strip 'Stangs I have owned: 2

    Helpful (0) (0)

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