Hi There!
Saw your post from last year - did you ever buy a supercharger kit for your 928?
Also, you might have seen the new thread on the Rasant Products kit, correct? We're installing one on my own car - Rasant bought the original designs from VCB Engineering, but w're reworking the kit to make improvements.
The Rotrex is EXTREMELY efficient as compared to other supercharger designs.