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The Dundon D4 Package is the culmination of our work on perfecting and guiding the pressure waves into and out of the 3.8L Engine resulting in 72lbft max gains over stock and 100whp at the rev limiter.


The Street Power Package is for street driven GT4's and Spyders and includes 200 CPSI Cats and retails exhaust valves.  You can choose to purchase a 997/991 GT3 muffler on your own, or purchase a lifetime muffler in Loud or Quiet with PVD Black Tips or Optional Titanium Tips.


Bottom Line on the below graph is a Stock GT4

Middle Line on the below graph is GT4 with Dundon Race Headers and Pro Tune

Top Line on the below graph is GT4 with the Dundon D4 Kit.

  • 72lbft gains at 5000rpm over stock
  • 320lbft at the wheels peak torque
  • 62 peak hp gains at the wheels
  • 70+ whp gains at 5000rpm
  • 70+ whp gains at 7000rpm
  • 100+whp gains at 7700rpm


This kit is fully bolt on, and completely reversible.  

Works for 981 GT4, Spyder and 981 GT4CS

The Kit consists of:

  • Dundon Race Headers - Proven 4th tube technology aids in suction wave strength giving our headers the most power.  321 Stainless, fully purged TIG welded construction and a lifetime warranty
  • Dundon Valved GT3 Muffler Adapter (w/ optional 200 CPSI Cats) - Replaces the stock muffler with 2.5" 321 Stainless Steel over axle pipes, Valved GT3 Muffler Connectors (your exhaust button still works).
  • Cobb Accessport with Dundon Pro Tune - The standard for handheld tuning devices, allows logging, flashing and converting back to stock with ease (you can even resell it later to another 981 owner).
  • Dundon Intake Runners - Directing and timing the pressure waves coming into and leaving the engine is what we do, the Dundon Intake Runners show this and enable large gains, carrying power all the way to redline, where the stock intake runners fall flat.
  • Dundon Lifetime GT3 Muffler (optional Quiet Muffler) - Our bullet proof 321 Stainless Steel muffler with correct length GT4 tips, comes in 2 flavors.  Loud is a bit more aggressive than an OEM muffler but with the drone cancelling upper pathway, and a full 3" lower pathway with an X pipe for the tip outlet (further enhances scavenging).  Quiet for those cars that run on dB-restricted tracks combining Cats and a Quiet Muffler is a great way to "fly under the radar" and keep the car's bravado reeled in!