Im wondering if anyone in this LS1 section can help me PLEASE!!!!

I have a 98 Camaro with an LS1 that im having problems getting the engine light to come off.I put a scanner on it and it said upstream O2 sensor so i changed them both with no luck the light came back on in a few minutes,so i put the scanner on again and it said O2 sensor again so i thought it were the other two so i changed those to only find out that didnt cure the problem

I put the scanner on once again and it said O2 sensor and air pump,so i tested the air pump and it is working fine,i thought maybe the check valves on the air pump hoses were bad so i changed them both with no luck again the luck came back on again.I have a SLP exhaust on there now that worked ok before this problem accured.The car works fine when the light is one so im stummped and im resdy to take it to the dealer and pay 95 bucks but i think it is a small thing.

Also the oil dipstick comes out a little bit when i come onto it,oil does not go up the dipstick at all.I changed the pcv valve and it does the same thing.Any answers or suggestions would be appreciated.

Thanks BradLS1