Mines mapped too, not overly much only around the 170 figure however the turbo still failed after a few months of being mapped. Think it gave up on around 68k.
Tbh I never thought I'd like a diesel as much as I do with mine, and like you have been saving for an S3. However I'm not fussed by not owning one yet as you never realise just how good these tdi's are until you actually own one.
Only other things I know of is they don't like hid's unless it's the well-done version, which there's a group buy on them at the min, pretty rubbish clutches but withstand 170-180bhp and cylinder heads cracking which apparently wasn't an issue on the 2006 onwards ones. You can check, if you've got a revision C head there are no known cylinder heads that crack. That's pretty much it I think hah