I post this before but no one reply. Anyway, I have OBD0 engine have 2 O2 sensors,with 1 cable each sensor. one on exhaust #1 & #4 and the other one on #2 & #3, both before the collector. The ecu also have 2 pin for o2 sensors the primary pin C16 (white cable) and the secondary pin C8 (red/blue cable). My questions is which O2 sensors goes into the primary pin (C16 pin), the #1/#4 or #2/#3? Right now, I just wiring those two O2 sensors together to pin C16. Does this will cause any problem? Thanks.