I recently bought a 99 Z with 105000 miles. I haven't really drove the car hard because i'm a little worried about the oil pressure. Cold it's just over 40 psi. After warming up I would say it's about 25-30 psi. I noticed a knock at 1200-1500 rpm every now and then. What are my options? Should I change the oil pump and o-ring? Maybe the barrings too? I have heard the early LS1s had o-ring problems. I don't know when the oil was changed before I bought it so I changed it about 1500 miles ago. Any help Please....

 

Could also be the oil sending unit.

 

start with the simple. get some lucas and change the oil. your oil pressure sending unit breaking will make your pressure peg out.