Boarder Line Low Oil Pressure

I agree with you. The engine does have a issue big time. Do you believe in the use of full grooved main bearings? I could've misunderstood you but I thought that earlier you said that they are a good idea and yet in post 21 your saying that they are not good for oil pressure.
How do you know? You do know "Some Engines" are built loose right?
It may have been built for thicker oils.
Sending a sample out would also be on the list when you swap to a heavier oil.
The report will tell you a lot.