Just bought a car with the PVC unhooked and it left a substancial puddle every time I parked it in the garage even if I didn't beat on it. It would be hard to ignore. Also, it smoked every time I nailed the excellerator. Your problem seems to be more internal. Is this a Chevy engine? They have the PVC in the valve cover. Makes a difference because Chevy doesn't have the rear main problem as much. More than likely valve guides. Many builders do a poor job on the heads. You probably have at least one guide/seal that is really bad, fouled the plug and doesn't even combust the oil anymore so no smoke. I would give it a compression check. If it has good compression focus on the valve guides and seals. A close look at the plugs will narrow down the problem. You said your plugs were not fouled but the oil has to either go past the plugs or on the floor.
Jim