Trying to identify a part that may be broken. I have a 2005 A4 2.0 Turbo.
There is a plastic elbow that attaches to some gizmo on the back top of the engine (Inline with the rear of the cam I believe) It has a vacuum line that runs to the brake booster and also t's off to some where else. The part bounces like crazy when the engine is cold. I can hear air being sucked in as well. I believe it is the cause of my rough idling. Can you name this part?

 

Can you post a picture? I'm thinking it could be the PCV (Positive Crankcase Ventilations) Valve.

 

Thanks Dave. I discovered a video of someone with the same problem. Turns out to be the vacuum pump. The molded hose connecter flops around in the housing until it is warmed up. I'm going to try to dismantle and silicon it in place.