It sounds like he means it has a surge , when he lets off the gas. above
2000 rpm. But he says the car stalls too.  So maybe the ecu is sensing the
stall and adding the surge to compensate... Sometimes it stalls because the
ecu couldn't keep up. Unfortunately I don't work on gas VWs much. I failed
miserably trying to make a cis  VW  run correctly I got for a song and a
dance. And I never recovered. So I leave them be.  I do believe the 94 2
litre has a throttle position sensor. I look at the tps as a rotable as they
are used all the time and move. So they wear. I,ve had a string of successes
replacing the tps. either it fixes it or reduces the problem. If you mean to
try parts , I think they aren't too expensive. there is a test in the
Bentley with a ohm meter for the tps. . a fuel pressure regulator in the
fuel rail.  cost about twice as much as the tps. there's a very expensive
airflow meter.  which may cause problems if its sooted up , or has oil on
it. Cleaning may do something. Anything beyond that requires somebody else's
expertise. If you do want a tps, get the part number off of it. there are
many different ones on the same exact VWs. I have difficulty with your
electronic diagnosis failure.  It is rare for an analysis to fail if done
correctly. If there was a failure to diagnose I wouldn't pay. If I wasn't
paying for it, I wouldn't think it was any good either. If there was a
failure found I,d let them fix it. If the cars stil runs like crap. I
wouldn't pay for anything until they finished fixing it.  Good Luck