I am new to the audi world and i just bought my used 2000 audi a4...i was taking off a cover on the engine and i hit a hose that was apparently very brittle. Needless to say it broke. It looks like a vacuum hose but i am not sure. It connects to a plastic tank that looks like 3 *****, its blue, and sits in the engine bay just behind the headlight the hose travels out the tank and up over the driver side valve cover. Any ideas on what the tank is, what the hose it, or any information.

 

I am thinking it is the vacuum resevoir. Can anyone confirm that?