ive read a few threads on rs246 about dodgy custom-code (i think) maps, including a few where the tuner took a proper huff because the customer posted some vagcom logs on the forum and asked people for their opinions of them after the remap.
The logs showed it well down on power and suffering from severe throttle cut...
Anyway, its not worth 6k imo. Its needing paint and an exhaust, your going to find it difficult to get a good paint match, even if you spend a lot of cash, and there are S4's around in good nick for less money. It is well specced, with the recaro seats and the RS4 exhaust parts, but unless you can knock him down a long way from 6k, then i wouldnt bother.