[pwd72s]

I've been trying to think of ways that would explain the ebay ad claims. So, I sent the link to a friend. This friend doesn't wish to have his name posted on the boards, but he has given permission to post his email response:

"Taking the top off reduces the weight of the car and allows the air turbulence to create a vacuum effect that actually pulls the car along permitting the higher top end.
As with hp ratings, Porsche was very conservative with their rev limits.
Part of it was a simple financial matter.
VDO had done a run of thousands of tachometers for Porsche based on early estimates. When the engineers informed management that the rev limits were in fact much higher they were simply told to design a limiting device (rotor) to keep the engines in the range of the already produced instruments to avoid the cost of designing a whole new batch of tachometers.
Most insiders know that the key to the rpms currently attained by the F1 engines (19K+) is simply due to removal of any rev limiting hardware."