Depends on the roads and driver alot, add into that most s3 now have air leaks everywhere, have you scanned it and sorted all the problems its probably got? Then like tuffty said, remap it.
A corsa vxr does a quarter mile in 15.0s at 94 iirc a healthy stock s3 does it in 14.7s at 95.
Besides any car can beat another with enough cash thrown at it, theres a vxr near me at 450bhp! Throw some cash!-)