LS AzZkIkr

I cannot figure this out for the life of me. I have been searching this site and have found plenty of writeups on the gsr swap in a vx but i was just wondering if its the same for a LS swap? I know i dont have a knock sensor and the butterflies that a gsr manifold has but i always get a O2 code! I have spent $150 on a new O2 from the auto parts store and several from the junk yards. I have changed ecu's also and have had no luck. The harness is in good shape(no cut or burnt wires). Has anyone run into this issue? THANKS