Dude what are you saying..... O2 sensors pre intake manifold?

O2's are in the OBD II system pre cat and after cat to sense a failed cat converter or exhause leak or engine that is creating to much polutents.

O2 sensors.....Exhaust side of the engine.... not intake side.

Bosch make an excellent book on OBDII engine management.... Really good read if you are serious about modifying a OBD II vehicle. I also have a full Crossfire Service manual CD if you need more help.

Out ChrisG