Alright guys and gals, I have one for you guys. A few days ago my car started knocking and the oil light came on, I thought oh no I'm screwed. So I got the car home (half a mile away) and shut it off, and shut it off to coast most of the way. When I got home I check the oil, and it was not touching the dipstick. So i added some and to my amazement still same symptoms. I crouched down hoping I wouldn't see what I knew I'd see and yes you guessed it, oil pouring down onto the ground. After searching and just deciding to just dig in with a few ideas what the oil leak source was I discovered the oil filter gasket had a crack in it, as well as the oil cooler gasket the is held in place with a large nut connecting to the oil filter housing. I immediately called and ordered the gaskets and started tearing it apart. I got all the way to getting everything out but when I disconnected the housing from the block something fell out. To my amazement it seemed to be a one way spring loaded check valve that looks like it screws into the port going to the turbo feed line. My guess is its to keep oil from draining the line dry and keeping the turbo from having a dry start. Only the lord knows how longs its been loose and blocking one of the main ports. My question is, am I correct on what its for and when I put it back in, do I tighten it all the way? I've never seen it and the several people I've spoken to have not seen this. The car is a 99 b5 1.8t AEB FWD. Here are a few pictures of the housing, where the valve fell out of and the valve itself. Thanks guys !