What should the oil pressure be on an 1988 MK111?

[mirage83]

At idle the oil pressure should be somewhere around 5 psi. Above idle the pressure will generally increase about 10 psi per 1k of rpm. So say at 3000 rpm you'll probably see something around 30 psi.

That's a stock system of course. Any oil system mods (and there are several) could effect your readings. I'd find a good reputable mechanic and put a direct-read gauge on there to find out what your pump is really doing if you're concerned about it.