Hi Ricky,
I also own an Octavia RS that has been tuned to 240 bhp by PETE's. So, initially the A4 in stock form, was quite a laggard in comparison.
I still have a few months on the warranty left; got it remapped 2 months ago. The Audi guys cannot detect the Remap, as it does not show up in their diagnostic s/ware. Only if they were to drive the car a fair bit, would they figure out that its quite different.
So far, the A4 has been fantastic. I am looking forward to the new A4 ( 3.2 FSI Quattro )!
Cheers!