This has undoubtedly been done by now to solve the problems on the
vanagon in question, but I had the problem of terrible idle and
terrible running that drove me crazy after redoing my head gaskets
two years ago. I solved the problem by accident and thought I would
pass it along.

If your car has the anti-bucking pigtail to the air meter, then open
the connection between the original cable and the add-on pigtail. My
problem was very, very slight corrosion in there. In checking all the
connections the first, second, third, fourth and fifth times, that
connector got overlooked.

Good luck,

Jim