You bought the car new right? I think when you go in for any warranty work or scheduled maintenance the Audi dealer scans the computer and if they find evidence of chipping they can deny coverage under the warranty. Not sure though.

May want to look into GIAC because they have this "Flashloader" dealie where you can switch back and forth between the stock program and the hopped-up program. I dunno if any of the other chip companies do that. I'm sure some of em do. So I'd get one of them switchable chips.