I recall seeing in a samba post (or maybe here) the exact measurements for the grease caps and hubs and how much wheel material needed to be removed.  They also listed a NAPA part # for a cap that fits but is not as thick as the vanagon ones.  Maybe you have an aftermarket grease cap on one side.

The thread I receall was from a guy who bought wheels on a whim and was asking how to make them fit.  I think he gave up after some discouraging (and over-reacting replies).  You may also have issues with the length of the stud/bolt for the Audi wheels, I don't know.  I did on the Mercedes wheels I modified.  It is a cheap way to get nice looking wheels, but a PITA to me and the only reason I would do it again, is now I have the drill bits.  15" VW of South Africa Rhein wheels look pretty good.

Dave in Fort Collins

--- On Fri, 1/14/11, J Stewart <fonman4277@COMCAST.NET> wrote:
> All I know is that the wheel that I
> ground the lip off of fits over the grease cup on the
> passengers side, but won't fit on the drivers side. Now,
> this experiment took place in my driveway last night in the
> dark, in the cold, after a 12 hour day at work. I didn't
> have time to put the van in the garage and check it out
> further, but I will this weekend. ...

>... you can't argue with German engineering-ever...

Exactly.  95 hp is perfect for a 2 ton vehicle.