i just purchased a 2000 gti 20v turbo. When you step on the pedal to accelate if you step on it all the way it will accelerate very slowly....if you barely tap it the car will respond better...once the car hit 4,000 rpms it will completely stop accelerating...only when you step on the pedal all the way though..if you barely step on it this wont happen....anyone have any idea what it could be??? thanks...