The idle could just be set a little high no? 84 rabbit, i cant think if those pumps had an idle booster on the backside that was activated with the cold start lever.
get it running and let it warm up for a few minutes. Take both fuel lines off and run them both in to a fresh gallon of Auto tranny fluid. run it on that for 10 minutes, shut it down and let it sit for an hour or two, then start it up and finish the bottle. switch back to diesel.
little cheaper than diesel purge, and probably does a better job of actually cleaning.