No oil pressure until truck gets up to temperature
So i have an 01 dodge ram 1500 5.2L. I recently changed out my plenum (easier than I expected). After a couple of weeks, now when I first start my truck I have no oil pressure for about 30 seconds then it comes up to almost 40psi. If I try to step on the gas before my truck gets to normal operating temp, my oil pressure guage drops down to 0 again. I'm confused if I need to replace sending unit, oil pump, screen, or what.