There is a limit to what the clutch, torque tube, transmission, and half-shafts can take. I understand the limit of the stock drive train is the main gear shaft in the transmission @ 500 ftlb at the crank.
The nice thing about the 928 is that V8 has so much low end torque that gearing is not an issue.
I can actually get a better lap time taking corners in a higher gear because I can power steer through corner exit (carry the 4 wheel drift out of the corner) without having to upshift until the car is going straight.