o2 sensor defouler / spark plug defouler

[aaronng]

yes code is o2 sensor

That means your O2 sensor is faulty. It is not caused by your exhaust being too rich. The single O2 sensor on your DC2R is supposed to read Rich/Lean. On newer OBDII cars, there are 2 O2 sensors, the 2nd one is meant to check if the cat is failing. So for OBDII, you can use a defouler on the 2nd O2 sensor to avoid CEL when you use a high flow cat. But there is no point putting a defouler on the 1st sensor because it reads rich/lean instead of cat pass/fail.