My neighbour's 82 aircooled Westy has an elevated idle
speed (~1000 rpm) but otherwise runs perfectly.  

        The idle is not affected by the bypass adjustment screw.  
The idle will drop down if I temporarily physically starve the air 
supply with my hand, leading me to believe that the butterfly 
valve on the throttle is worn sufficiently so as to allow too much 
air to pass by it, even when in closed position at idle speed.

        Am I on the right track?  Is this part available anywhere
other than VW?  Is there anything else I should know?

        Thanks.

Gary Meek
82 Vanagon td
83 Quantum td