[nytrainer]

I think it's time for the next step and mount the fittings in the back/top of the block and plug the oil filter adapter or re-install your electric gauge sending unit if you want (though you now know it's accuracy or lack of it ). That will tell the real story as to what is happening in the various rpm ranges (instead of wondering if the bypass is open at the higher rpm causing the possible lower oil pressure readings that you're seeing then).