There are three adjustable screws on a Bosch VE pump. I know the low speed and the max speed that stop the throttle plate. What's the third one do?
If your referring to the one with the 13mm lock nut on it and a slot for a flat blade screw driver in the end of it that's the MAX fuel screw.
Can it be turned up to get more fuel at top end. My 91 jetta 1.6 NA seems a little fuel starved. My Mercedes 300D had an adjustment that one could achieve a little black smoke on heavy acceleration. Would adjustment this the same do you think?
The max fuel screw should give you more fuel (and smoke) through the existing powerband. If you actually want to rev higher you will need to alter the governor.
Cranked the MAX FUEL screw in 1/4 turn before driving home from work and it seems better. I'm going to keep increasing 1/4 turns until I get a little black smoke.