Confirm you're getting a genuine TTS — the gauge cluster should show the 'S', a 6800-rpm redline, and a 180-mph speedometer (some cars have a regular-TT cluster). Then check the Magnetic Ride dampers (costly if failed) and tire date codes, since low-mileage cars often wear old rubber. …
Verify the TTS spec, Magnetic Ride, and tires
Audi TTS (8S) · buying-advice