Hmmm...old thread but exactly what I needed. Have a CA car but I used the Fed exhaust as well. I also have the BPW4 ecu. Instead of stripping back the engine harness to get the pre-cat O2 sensor to reach the down pipe location, I just used a federal engine harness I had. Now I realize the ECU is looking for the 2nd O2 sensor(CEL)and I'm not sure if I have a place in a harness to plug one in?? Hope this makes sense and I can get some insight?
You CA harness should have had a plug under the driver seat just as the federal did that is where i plugged in the second sensor on my CA car.