I just wanted to share some info about the catch can I put in my MK1 a while ago. I finally had a look inside it after about 10 hrs of running time. Much to my surprise there was about 200ml of oil in the bottom, I wasn't expecting much at all. So there you have it.
 

Are my eyes deceiving me or have you got the brake booster hose going through the catch can?
 
If you have that isnt how it should be!  You should just have the hose from the block breather and perhaps the rocker cover breather going to the can.  The booster should go straight to the manifold and nowhere else.
 
G

In the photo above the arrows show direction of vapour flow. The brake booster hose is the blue, PCV hoses are yellow and manifold vacuum is red. 
 
It's just the same as the factory plumbing below but with a catch can and heaps more hose! It's probably not worthwhile doing it to a bog stock motor but my manifold vacuum is from 2 runners instead of all 4 like a factory manifold. I've read somewhere that an imbalance like that can cause problems so I installed the can.