My mechanic diagnosed my 4000 rpm idle as a failed "idle speed control unit."
 (ouch $250.00) While investigating this however, he said another FI
"control" component on the 87 Westy didn't match the VW part number.  He said
it came from an AUDI 5000 and suspects it was replaced by the PO.  He said
that part may have to be replaced as well.  Expensive!  Should I just wing
it?  If it worked with the Audi part in the past maybe it will work again.
 I'll know after the idle speed control unit is replaced.  Here's the rub:
The mechanic said the AUDI part could have caused the other part to
fail...but then again it might not have.  It it does cause the idle control
to fail that's another $250 down the tube.
Any thoughts? Anyone else with computer problems like this?