I think the same Aux Air Regulator is used in Saab 900s, Rabbits, and just
about any other vehicle with Bosch FI.  I successfully migrated one from a
Saab to a Rabbit , and then to my 914.  Shouldn't be too hard to find
another one.  I also took mine apart, cleaned it with WD-40 and put it back
together with a little super-glue.  Make a mark on it so you can line up the
"innards" with the "outtards" later.  A flashlight works to see if it is
opening and closing...

Matt Sim
'81 Aircooled Westy
New Cumberland, PA