Sorry I am late to the party. I have read all the post and by chance have you confirmed this high reading with another gauge? Are you sure the gauge is not giving false readings?
If you have, I think you need to have a very close look of the engine to see what the issue is.
When my 261 is cold, the oil pressure will peg my gauge in the truck, (still running the 30 psi stock gauge). Only after some longer driving will the oil pressure drop down to 15 psi at idle.
