Thanks, guys. Since I have to add ballast to make weight, there seems to be no reason for me to go w/ an S4. However, it looks like I will be buying my old car back and it is an S4 w/ S5 engine. Can an S5 AFM be spliced into an S4 engine wiring harness and run off the S4 ECU? Worth fooling w/? Any idea how much performance may be lost w/ S4 ECU? Chris, I suppose that the fast S4 cars had actually been stripped and converted. Changing the body wiring harness in situ would be a major hassle - do you think anyone has actually done that?