My 2003 (facelift model) S3 has been chipped using One Click for the past 7 years or so, and has been awesome. It had a great torque kick low down around 2500 rpm, then really set off around 3500.
Over the past couple of months it has lost that low end kick and really only pulls hard from 4500 - feels more like the standard engine.
I have tried the one click to re-download the chipped map, but no difference. I tried this as the car had some work done earlier this year (none on the engine) and it might be the case that the lower torque was evident after this work (work not done by an audi dealer, but our local village garage that have looked after it for years)
The car also had developed a sort of 'stutter' around 3000-3500ish when accelerating moderately in 4th or 5th and i cleaned the MAF which has helped this.
I reckon the car is down around 1s to 1.5s on 0-60 too