Just installed a b18c5 swap in a 93 cx with a p28 harness and the car is in limp mode. The fuel is cutting off at 6600 rpm and is throwing a cel #1 which is the o2 sensor which is located on the header if I'm not mistaken. Could just the 02 sensor be causing all this trouble.

 

harness wiring more than likely.
but it could be a bad O2.

Also, there is only one O2 in an OBD1 car.