Hi guys again,
I was looking at the Volkscafe website and found a Diagnostic Tool there, specially designed for Vanagons.  It seems to do the same kind of things what Mr Boehler's does and I wonder if it is one of his designs too.  Any of you have an idea how good it is and if it is worth the money.
I don't even know what the price of it is.  
Zoltan