After the winter break I started the Volksback for the first time. Unfortunately, the doubts I had about the low oil pressure were confirmed. So. I had to remove the engine again, to fix the problem. But what IS the problem? I used the "wisdom" of the internet and also a forum which I think is a good one, especially when it comes to engines and issues with engines: http://bugfans.de/forum/~
The answer to my problem is (hopefully) the oil pump cover gasket. In the Victor Reintz engine seal kit, this particular seal is made of a superb material, but way too thick! it is ~0,3 mm, which allows the oil pressure to decrease drastically. I checked what else I had in my parts stash and found a 0,1 mm "paper" gasket:
this would be a step in the right direction, but after measuring the gap between the gears and the housing - which was 0,03 mm - I decided to use the Loctite 574 only.
The problem on the Type 3 is the fan and housing, the whole engine needs to be stripped in order to fix the oil pump - maybe not this much, but I checked some other things at the same time.
But with the engine out anyway, I made the decision to finally tackle the IRS subframe installation...