Hi,

I have noticed some oil residue below the oil filler neck.

I think it is coming form the pipe I marked in the pictures below (sorry for the quality).

Where does the pipe should go to?
Should it be vented?

The car had the emissions removed by the previous owner. It is a 1989 EUDM Turbo II (S5)

 

I would route this pipe to a catch can with a breather / filter on top.

 

Oil does like to leak in those areas. Check the hoses attached to the filler neck, as well as the gasket/o-ring at the base of it.

As far as that vacuum line is concerned, from looking at my lines right here, it looks like one of the lines for the boost control solenoid (has the vacuum line with 9c labeled on it in your picture). Make sure those are still connected, as you will have the symptoms of a boost/vacuum leak otherwise.

Hope this helps.

 

You are 100% right, sir!

It was the "9C" unplugged. I don't know how I could miss that.

Many thanks!

 

I'm in the process of color coding all my vacuum lines, so I know where they go and how they connect to each other. If you are bored and have some model paint, its a pretty good idea. It keeps you from having to remember where everything goes, even if you've messed with it a bunch of times.

 

Hope it's not the rear iron...