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  1. Flowmaster 99-04 Mustang American Thunder Catback w/40 Series Delta Flow Muffler
    $525.95

    Flowmaster 03-04 Mach-1 Catback w/ 40 Series Delta Flow Muffler

  2. 2.50 Dia. Tubing
  3. 5.00 X 10.00
  4. American Thunder
  5. 3.00 Stainless Tips
  6. Dual Out Rear


  7. Flowmaster's systems will improve acceleration and passing power, as well as help improve fuel mileage. Every system is individually engineered and dyno-tested for each application and includes all required mounting hardware. All tubing is mandrel bent for superior exhaust gas flow, and is a key to the system's performance improvements. Both mufflers and tubing are fabricated from aluminized steel for corrosion resistance.

    American Thunder
    Looking for the famous, full-on "Flowmaster tone?" Look no further. This American Thunder system will deliver the aggressive tone you want, as well as the performance you demand.

    Delta Flow Technology
    Developed from Flowmaster's line of Delta Force race mufflers, Delta Flow technology provides superior scavenging of exhaust gases even over a comparable (standard) Flowmaster muffler. This results in increased horsepower, torque and fuel economy, along with reductions in exterior sound levels and interior resonance. These three deflectors function properly only when they've been precisely placed and welded to exact specifications. Together they provide superior reductions in exterior sound levels as well as resonance transmitted through the exhaust system and into the vehicle. Learn More
  • Flowmaster 99-04 Mustang 409SS American Thunder Catback w/40 Series Delta Flow Muffler
    $643.95

    Flowmaster 03-04 Mach-1 Catback w/ 40 Series Delta Flow Muffler

  • 2.50 Dia. Tubing
  • 5.00 X 10.00
  • American Thunder
  • 3.00 Stainless Tips
  • Dual Out Rear


  • Flowmaster's systems will improve acceleration and passing power, as well as help improve fuel mileage. Every system is individually engineered and dyno-tested for each application and includes all required mounting hardware. All tubing is mandrel bent for superior exhaust gas flow, and is a key to the system's performance improvements. Both mufflers and tubing are fabricated from aluminized steel for corrosion resistance.

    American Thunder
    Looking for the famous, full-on "Flowmaster tone?" Look no further. This American Thunder system will deliver the aggressive tone you want, as well as the performance you demand.

    Delta Flow Technology
    Developed from Flowmaster's line of Delta Force race mufflers, Delta Flow technology provides superior scavenging of exhaust gases even over a comparable (standard) Flowmaster muffler. This results in increased horsepower, torque and fuel economy, along with reductions in exterior sound levels and interior resonance. These three deflectors function properly only when they've been precisely placed and welded to exact specifications. Together they provide superior reductions in exterior sound levels as well as resonance transmitted through the exhaust system and into the vehicle. Learn More

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