[Swiss*Jet*Pilot]

The Audi TT (8J) 3.2 VR-6 (BUB) PCV is located inside the Valve Cover "hump" directly behind the oil cap. Inside that hump, you'll find the Cyclone Oil Separator (COS) and inside the COS you'll find the PCV diaphragm (Vacuum Valve). Unfortunately, neither the COS or PCV diaphragm are available as individual replacement parts. Instead Audi will happily sell you the entire valve cover for around $425 (USD).

This post from the Audi TT Forum UK will explain how to replace the OEM vent tube and install an external PCV vent tube from a VW Toureg, effectively by-passing the internal PCV, and save yourself a ton of money in the process.