I recently saw a thread in which someone added a pic of the vacuum line from the manifold to the DV highlighted in red, with a link to another sight with all the vacuum lines highlighted. My vaccum lines are looking old and worn, and I wanted to replace them as my Saturday project while the wife was at work. I heard a vacuum leak can cause the engine to run rich. A recent scan indicated that I've been running rich, and I can definately smell it when I first start the car.
Can anyone remember where this thread is? I can't find it for the life of me. Thanks guys...

 

I found this that might help you out. I was thinking of doing this myself soon, but I'm trying to figure out whether to get 5/32" ID or 3.5mm ID hose. Aren't they about the same?

 

a vacuum leak will cause you to run lean. a boost leak will cause you to run rich. a broken vac line will cause both things, because it will be a boost leak while pushing the gas pedal and a vac leak at idle.

 

I bought a few feet of 5/32. I think it's slightly bigger, but still a good fit. A couple zip ties (heard no one has every used those on an Audi before) just to be safe.