I have a 93 with the LT1, 114,000 miles, no mods. I have fixed the intake manifold leak at the rear of the intake twice in one year. The last time I did the repair I installed a valve cover vent in the valve cover instead of the oil fill cap.
The vent causes the car to idle a little ruf but it has kept the gasket maker form blowing out again. Last week I decided to test it and took the vent out and reinstalled the oil fill cap. After about a week of driving the car, I checked the seals and saw oil residue at the rear and front of the intake manifold. It seems as if there is excess pressure building up and blowing out my gasket seals. I have replaced the PVC valve and the EGR valves and dont know what else to do.
Thanks for any help.

if PVC is working properly, you should not have excess pressure in crankcase. remove the fill cap while idling, see if you see puffing if so rings are gone thats blow-by

do you mean look for puffing smoke coming from the oil fill cap?

do you mean look for puffing smoke coming from the oil fill cap?

First take off the hose at the PCV Valve an see if you have Vacume. If you have Vacume. Then make sure the valve cover is not clogged were the PCV Valve Goes. Check that out an let me know your answer an then I can Help you Further.

do you mean look for puffing smoke coming from the oil fill cap?
yes exactly, if you do then rings are leaking but if not then your PVC is probably not functioning properly pull it out of cover while running ,put finger over end to see if it is pulling if not check for cracked hose clogged line ,disconnected etc.