Finally got it installed today, and yes, it does seem to smooth out some peaks and a flat spot around 3000 RPM. Not sure if it placebo effect or not I'll see in the next week or two how it gets along with my APR chip.
So far, I've driven about 150 miles and no CEL.

 

ive never had a problem with mine.

 

On my '03 A4 with the race valve installed and running APR 1+ I got CEL for boost request and boost received. Since I am changing my turbo in a few days, I have decided to get my hands on the N75 race and GIAC FXK04.

 

which turbo are you upgrading to ?