Flowmaster Cat-Back Exhaust Kit American Thunder 2-1/2” With 3” Stainless Steel Tips GT 1999-2004/Mach 1 2003-2004

98% of 100


  • 16- Gauge Tubing
  • Aluminized Steel Construction
  • Super 40 Series Mufflers
  • Moderate Exhaust Sound
MSRP $713.00
You save 10%

Flowmaster 2-1/2" American Thunder Cat-Back Exhaust Kit with 3" Stainless Steel Tips for 1999, 2000, 2001, 2002, 2003 and 2004 GT Mustangs and 2003-2004 Mach 1 Mustangs.

If you have a 1999-2004 Mustang and you're looking to replace your original exhaust system and add some horsepower to your Mustang purchase this 2-1/2" American Thunder Cat-Back Exhaust Kit with 3" Stainless Steel Tips from Flowmaster. This Flowmaster Exhaust system is a direct replacement for 1999-2004 GT Mustangs and 2003-2004 Mach 1 Mustangs.

Kit Includes:
- Pair of Flowmaster Super-40 Series 2-Chamber Mufflers
- Pair of Aluminized Steel Tailpipes
- Pair of 3" Stainless Steel Tips

- 16 Gauge Tubing
- Mandrel Bent Piping
- Moderate Exhaust Sound
- Mounting Hardware Included
- Aluminized Steel Construction

This American Thunder Exhaust System is constructed from 16 gauge aluminized steel. The exhaust pipes are mandrel-bent, this allows the exhaust to flow without any restrictions. Flowmaster installs a pair of Super 40 Mufflers on this American Thunder Exhaust System. With that being said the mufflers will provide a moderate sound for a classic muscle car sound.

When you install this exhaust you will experience improvements in acceleration, passing power, and fuel mileage. The 2-1/2” mandrel-bent pipes run all the way back to the rear which allows the exhaust gas to escape from the 3” stainless steel tailpipes. Flowmaster uses aluminized steel pipes which features great corrosion-resistant qualities.

Flowmaster is a manufacturer of just about any part you need for your Mustang's exhaust, from full exhaust systems and exhaust kits, to mufflers and accessories. Flowmaster is widely known for their distinctive 'Flowmaster sound,' which is available in mild, moderate, and aggressive tones, so you know you can find the perfect muffler or exhaust system for your Mustang.

Purchase a new Flowmaster 2-1/2" American Thunder Cat-Back Exhaust Kit with 3" Stainless Steel Tips for your 1999, 2000, 2001, 2002, 2003 or 2004 GT Mustang or 2003-2004 Mach 1 Mustang from CJ Pony Parts today!

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Related Categories: Mustang Parts, Mustang Exhaust, Mustang Cat Back Exhaust Kits

Installation Difficulty


Intermediate skill is required for this installation.

Installation Videos

Video Transcript

So far I've added a BBK Throttle Body and Plenum as well as a JLT Cold Air Kit to our 2002 Mustang GT. These parts bumped up our horsepower and make the car a lot more fun to drive but it still does sound like a Mustang. Today, we are going to remove our factory cat-back and replace with this American Thunder Cat-Back from Flowmaster.

The basis for the American Thunder system is a super 40 muffler, a classic Mustang muffler gives the sound that everybody is familiar with. This system is a 2-1/2 inch system featuring Mandrel Bent Tail Pipes leading out to a pair of 3 inch stainless steel tips. Although, you probably don't need to hear what a stock system sounds like, we're going to fire it up anyway so we have a comparison for after. Yeah, it's just too quiet.

For this installation you’ll need a lift or a jack and jack stands, sawzall, 3/8 ratchet, 14 millimeter deep socket, 14 millimeter wrench, hammer or mallet, exhaust hanger removal tool and safety glasses. Once you get the car off the ground, the first step is going to be remove your factory exhaust system. It's going to be 1 piece all the way to the tail pipe so you have to cut behind here unless you want to remove the whole rear axle.

Now, we can remove the tail pipes from the hangers, take them off the car. Next, we'll separate the mufflers and flow tubes from our factory H-pipe. A little tap with the hammer to separate. Now, we can remove the muffler from the hangers. Now, we'll begin the Flowmaster installation by installing the tail pipes first.

Now we're ready to install the mufflers. We found by installing a bunch of these over the years cutting a couple of small slots in the muffler here will make it slide onto the tail pipe easier and give you a much better fit when you clamp it down. Now, we connect the muffler to the factory H-pipe. You can reuse your factory hardware if it is in good enough condition. In our case, we're just going to use some new nuts and bolts.

Now, we'll install the clamp between the muffler and the tail pipe. Just want to get it hand tight for now and make sure our tail pipe is where we want it before we tighten it down. It's lined up pretty good with our bumper so now we can tighten down the bracket. Now, we can repeat the process on the other side. Now let's see how it sounds with the Flowmasters on.

You got a nice deep tone you've come to expect from the Super 40 Flowmasters. The Flowmaster American Thunder gave our '02 GT a nice little growl to go along with the performance modifications we've done. Installation will take you around 2 hours. You'll be back on the road in no time.

Vehicle Fitment

This product will fit the following Mustang years:

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