Yes these engine have crankcase pressure visibly a lot some engines more then others. There is no set specification for measured pressure. The oil separator on drivers valve cover does a great job of separating oil and vapors as long as oil intervals ate being followed and a good oil being used. There is no filter in the oil separator its jist chambers (rat maze) type system. We have seen a couple trucks come in with plugged crankcase vent holes sludged due to oil not being serviced. Unless your engine is puking oil out of every seem, excessive oil consumption, turbo seal failures or even white smoke out exhaust. I would probably say system is working and pressure are within normal operational range.
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