Dundon GT4 Race Headers vs Competitor Race Headers
We tested our GT4 Race Headers bolted on vs a competitors GT4 Race Headers bolted on. No tune.
First a picture of the Stock Manifolds (left) Competitor (Middle) and Dundon Race (right).
All were tested blocking the hot air from the radiators and blowing cool air into both sides air intakes. Both were tested with K&N Airfilters and the Cobb Stage 0 (stock) map. Same SAE correction etc...
Dundon GT4 Race Headers vs Competitor - +25whp and +18lbft at 7100RPM
Dundon GT4 Race vs Competitor Race,
+29whp and +30lbft at 5000rpm
Dundon GT4 Race vs Competitor Race
+25whp and +35lbft at 3800rpm
Dundon GT4 Race vs Competitor Race
Dundon GT4 Race headers have superior performance, superior construction and use superior materials, you really do get what you pay for.. 
All Dundon headers are made with 321SS, the advantages of this are numerous and include, better fitment, higher heat tolerance, superior resistance to exhaust gas corrosion and a lifetime structural warranty to the original purchaser.
The headers attach to the factory PSE muffler and are quiet with no drone at cruise, but put your foot down and they're all kinds of flat six glory.
Dundon Headers are specifically designed for each vehicle and engine. Unlike our competition that uses a one size fits all, we tailor each system to the unique needs of each engine.
Gains Over Stock:
3600 RPM: +42 wtq
5000 RPM: +36 wtq, +34whp
5800 RPM: +15 wtq, +16whp
6500 RPM: +28whp
7000 RPM: +30whp
7500 RPM: +41whp
Our dyno read the stock car at 330.8 whp at 7400, Porsche rates the car at 385bhp at 7400, this is 14.1% loss with our Dynapack 4000 hub dyno running the car in Rolling Road mode using the factory PIWIS tools.
Dundon Race Header equipped GT4 is now at: 426BHP
GT4 Tunnel video
Dundon 991 GT3 Stage 2 chasing GT4 Stage 2
https://youtu.be/XpC3713d8wI