I've been restoring a 2000 NB TDI, and several people have worked on it over the last few months. I found a square rubber plug that someone removed from somewhere in the front of the car, but no one remembers seeing it before. The VW part number is 1C0971908A and it's about 2" x 2". I've Googled it with no luck. The front and back photos follow. Can anyone give me an idea of where this came from. Thanks!