Dyno work done at Powertrain Dynamics!!! ;JBA headers added about 13 RWHP 390-402 , torque stayed about the same. Im not sure if the headers were really worth the bucks, but the GT does run much smoother with better throttle response that is noticable in my opinion! Im happy to get 402RWHP and have an excellent tune! The GT runs great as a daily driver, and runs like hell when called upon!!!!!! Steve at PTD also said he hasnt seen much horse power gains with JBA's on NA GT's.