Testing?
If the vacum gauge reading, that you hook to the vacum pump, shakes or vibrates when the truck is at idle, that is OK there is no need for lots of vacum at idle. It's when the engine gets to 600 or1000 RPM that you need a steady supply of vacum for boost or EGR. Don't ask me how I know this. By the way does anybody want to buy a new vacum pump?
94 Chev Blazer, 6.5TD, 3.42, 4WD,Gear drive,,Remote FSD behind drivers headlight,,Mobil 1 in difs and trans,Rotella 30W, Over a quarter of a million miles !! Member -1.94 club.