The 68mm version is designed to function with the factory 68mm throttle body that was O.E. on all 996 factory Turbos. The 68mm Plenum delivers similar power as the larger 74mm competition Plenum. Horsepower gains range from 30 to 35 above the stock power band and initial boost response is improved. The IPD plenum delivers more power and more torque giving the 996 Turbo a stronger mid range and top end. The 68mm Plenum version is perfect for the Turbo customer looking to improve engine performance on both stock and moderately modified Turbos developing under 700 horsepower. The IPD 996 Turbo Plenum will truly transform the already impressive Turbo performance. The Plenum should be the first performance upgrade installed on any Turbo. They deliver great power gains on all Turbos whether they are bone stock or highly modified.