low oil pressure

I've got a pontiac grand am 2.3 quad 4 HO with low oil pressure.
I've had the crank shaft reground, new bearings, oil pump, timming
chain, sprockets, chain tensioner,cam towers and oil pressure
sensor. what could be the problem? Can anyone help???

Sadly, your Problem could be simple. Many cars with high mileage can get sludge build up in oil passages causing low or fluctuating oil pressure readings. I had the same with my 95 Grand Am...Try a motor flush u can buy at any auto store...It fixed my problem.....good luck