You need the O2 sensor!!! Get a downpipe that's made for the supra with the O2 sensor mounting flange.
The second O2 sensor is there for OBDI cars too, but as far as I know it doesn't do anything... Don't really know why it's even there, anyone know??mfh said:You don't need that 2nd O2 sensor. It exists only to tell the ECU whether or not the cats are in order. It only exists on OBD II cars, hence the MIL light going off when you remove your cats on '96+.
You can leave it disconnected if you want, or get an O2 sensor simulator circuit to fool the ECU into thinking everything's working fine.
Either way the car will run the same.