The second time the manifold was off. I removed the plug for the oil pressure port and also resealed that. I'm running the oil pressure sensor from a different location, the one your talking about just has a plug threaded plug in it. But I checked for leaks from there and it's dry.
I never thought about the crankcase pressure. I'm still using a pcv valve in the one vale cover and just a oil fill cap ( nonvented), in the other cover. Is that pressure that high that it could blow out the sealant.
I'm using just sealant along the back of the engine, also have and never had issues until now.