DeeGee, it is my definite opinion that you have serious vacuum leakage at the PCV Valve. -could even be a defective valve ?? The OBVIOUS clue is vacuum in the crankcase when you remove the oil filler cap. This should never be.
(-by the way, the "screeching sound" is caused by atmospheric air finding it'* way into the engine, past gaskets, crankshaft seals, and where ever else it can squeeze it'* way in). -just to verify, I'll bet the screeching goes away just as soon as you remove the cap.
If you haven't already fixed it, then I'd remove the pcv valve again, and inspect things real carefully.
(-you may need to find someone with the same design setup, and carefully remove and compare.)
Please reply back to let us all know what you found.