[bobcowan]

15psi at 2,000 rpm's is definatly too low. There's a problem some where. And if there's a big variance in in pressures, that's a bad thing.

The first thing to check is the gauge. Go down to Wally World and get your basic mechanical pressure gauge. All you need is the cheap plastic tubing type, nothing special. If you're getting the same readings in the garage, then most likely the dash gauge is correct.

Big fluctuations while driving usually means you're sucking air. Could be for a lot of reasons. You'll need to pull the pan and pump and inspect everything to see what's amiss.