Have a compression check done and a general inspection. 90k for Z is brand new in my opinion ;-). A lot of parts fail around the 80k mark, so they may have replaced those. Make sure the car drives at the normal temperature, look for full boost at around 3.5k. Make sure the hood is aluminum. Check the clutch for slippage. Check the timing, they may have advanced it to hide something. When they do compression, check that the spark plugs are the right ones for the TT. There's so much you have to look at these cars for since they have so many years on them by now. Definitely do the first 2, a lot of these engines have been overheat and may have bad compression. I picked up a 95 TT in Glendale only to find out it had 125psi compression on all cylinders. I didn't even start to speculate and took it back. It was bummer, because otherwise, that car was mint. Good Luck man.