I have a power loss, especially at higher speed on my S3! The turbo will kick in, hold back and then kick in again, like a really bad flat spot! It is under warranty, Audi plugged it in to reveal there was a reported 'Air Fault', but don't know why. They reset the memory and the car was running okay for a couple of days, but did seem a bit slower! Strange thing is; when I have the problem, the Turbo seems a lot stronger then hits that flat spot!
Let me know if you've had the same problem. Mine is a standard 210bhp 2000 (w).