Your problem does not sound like mine, at least.  Mine was due to the
coolant temp. sensor.

Actually, I think I know what your problem might be caused by, but can't
think of the name.  Maybe someone else can lend a hand here?  I remember
reading in Chilton's Fuel Injection repair book (they actually have a
chapter on VW Vanagons that was very informative!  Describes the
digifant, digijet and something else on various VW models with wiring
schematics, testing procedures, expected multimeter readings, etc--found
it at my local library).  The book spans several years and several
models of vehicles (U.S./Jap/German).  They give a thorough testing
procedure for testing the FI system (specific to VW) to find the source
of trouble, or at least to narrow it down.

Anyway, there is something associated with the throttle switch or
thereabouts that has, I think, the same reading for all the way open and
all the way closed.  (It's been a year since I looked at the book, so
I'm SURE I'm not remembering exactly right here!).  If this little
doohicky part is bad, it would be giving bad readings at the
in-betweens, i.e. your problem.  Maybe somebody knows what I'm trying to
describe.  If not, try finding this book, it might help.

As always, I may be way off.  Your description just hit a memory chord
and I think that's what I read (but my memory may be off key!)

Good Luck!
Tonya
87 Vanagon GL Wolfs
74 S. Beetle