Engine number
WARNING: This page is about a different car, the 2004 Volkswagen R32. However, it is still accessible from the selected car via links, so may be relevant.
The engine number "engine code" and "serial number" is located next to vibration damper on cylinder block under coolant pump.
Additionally, a sticker is affixed to intake manifold with "engine code" and "serial number".
The engine code is also included on vehicle data plate.