Does anyone know how much vacuum should be produced by the vacuum pump at idle in a '95 6.5TD?

Mine is only showing about 2" of vacuum at idle. I think this may be the root cause behind my EGR-related check engine light (code 32 and 33).

At 2500 rpm, vacuum increases to 20". I am hooking my gauge directly up to the pump, so leaky hoses are not the problem. 2" at idle seems really low to me.

Try shooting some WD-40 in the line and drive it some then recheck.

It should build up to 22"+ after a bit of idling.