Excessive backflow of PCV emissions into the air cleaner

Check to see that the pcv is actually working as it's the breather not the pcv. The hose or the valve can be blocked and should have intake vacuum. Then check compression with a leak down test. Also check to see if cylinder head drain back holes are blocked.

It sounds like a problem I had in the shop the other day, The truck was two years newer but had the exact symptoms you describe. Once disassembled, the engine had a broken top piston ring allowing the engine to fill with excess pressure. (It would cause the same problem if the piston is cracked.) Is the engine making any noise?

Best, Ken