So i'm about out of ideas, i'm hoping someone has run into this before and can help me out on something i'm missing:

The facts: Evo 9, 55k miles, Stock engine, 30R turbo, ARP head studs and Rod bolts. Idle set to ~800 rpms.

Last summer I had a low oil pressure light come on whenever it was at idle, hot and A/C was on. I changed the pressure sensor and the problem went away until the winter.

When the problem came back this winter I had the oil pressure tested and it was slightly low at idle but came up right away with RPM, my builder said not to worry.

A month later i was getting the light whenever the car was under 1500 rpms so I stopped driving it and changed the oil pump with a new pump for mitsuparts.net (as well as the timing belt and water pump for the 60k service). The shop also changed the pressure sensor again.

Drove the car about 200 miles no issues. 1 month later (today), I am getting the low oil pressure light again, only at idle. Oil level is fine. Car sounds fine.

Any idea on what it possibly could be?! Not sure what else is left to check!