u/Chebycheese

so I recently got a 2003 Tahoe 5.3 for free but it has low oil pressure at hot idle it about 3psi 2000rpm about 15-18psi, I’ve replaced the o ring in the oil pick up have a acdelco oil filter changed the oil pan gasket and I’ve changed the oil pressure sensor with a acdelco one and I’ve tested it with a gauge and it’s about the same as on the dash any ideas what wrong with it.