The head gasket would be the first thing I would check.
I never had a problem with the intake but I have followed some other threads where that was the problem.
I went thru the PCV value and yes you need one but that was not the problem.
I had someone rebuild the engine that did not know the difference between an iron block and alloy pistons. It smoked as it heated up because the expanision was different for the two metals. The rings never seated. A complete rebuild was the answer.
No problems for 5 years. Black marks whenever I want!
