That is a rear timing cover I wouldn't tear mine apart to put it back on but it could help keep some dirt and **** out. I hate to tell you to not put it back on, but I wouldn't do it until the next timing change. Considering how important that is and how much work it would be I would definitely wait.

 

Sweetness, well I tore it all down in a couple of hours yesterday. I put the part back in and now I'm putting it back together. What's up with Audi bolts, they are really soft and love to strip out. I had to replace a bunch of them yesterday. It was just the rear timing belt cover, it it looks like a bit of dirt had gotten in there. So I feel better about replacing it. Thanks Gents.