Low Oil Pressure when WARM. 1999 GMC Sierra 4.3 V6 "W"

When it's cold I can floor it and it'll go to 4K RPM.....When it warms up the oil pressure drops and then I can't push the motor over 1500 RPM. I overhauled it and used the old camshaft....I really don't want to get charged 80 bucks an hour for a mechanic to take 2 days to tell me it something I could have fixed myself.

This is killing me!

Are you saying the eng will not rev past 1500, or you just won't because of the oil pressure? You need to verify the oil pressure with a manual gauge.