DumpdEJ6

So I've got myself a little weird situation going on in my car. 1999 Civic Hatchback, semi-built LS-VTEC 1.8 engine. I'm not new to Honda engines, but I am at a loss here.

Ever since I built my engine, I've had slightly low oil pressure. It would be great on a cold start, but once it was hot it was idling at or near 0psi. I switched from 10w30 to 15w40 and that helped, it idled hot at around 10psi, which is where it was supposed to be. I should add here that when I assembled the engine, I ported and shimmed the oil pump for better flow. Now here's the weird part: One day, doing an oil change, I noticed that the dipstick was showing full after I put in only 2 1/2 quarts or so. I had also noticed that when I drained the oil, less came out than I thought should...car was level when doing the change. I checked and rechecked, it was showing completely full on the dipstick so, confused and hesitant, I started the car and then checked again. Still full, decent oil pressure. I've had zero issues with it since.

The next weird part: I blew up a synchro in the transmission at the track and changed transmissions. Oil pressure is now 80 psi at idle cold, and 20psi at idle hot. Changed back to 10w30 and same thing. I'm worried that it might be too high for the various seals in the engine and I especially don't want to have to replace a leaking rear main seal, kinda tired of taking the transmission off, lol.

I swear by all the car gods I didn't touch ANYTHING related to oil when I changed the transmission, but even hot, I am hitting oil pressure cutoff of 90psi at 4k RPM. From 4k on, it's just bouncing from cutoff to 80psi then back to the cutoff.

What the hell? Anyone?