UnderdogY'all could go back to my review and initial installation of the SC header.
Yes, it eliminates the pre-cat.
Yes, it causes this particular code.
Yes, you can make it happen less frequently with a defouler, but it still happens.
I quit worrying about it. My CEL is on most of the time, and I occasionally check the codes to see if there's anything new.
There is a second cat after the one in the (stock) header. The first one "lights off" quicker because it's closer to the combustion chambers, thus reducing start-up emissions. The second one still does most of the work after the engine is warm.
This particular code doesn't cause any other problems. Doesn't put the car into limp mode or anything. It's just informative, and telling you what you already know. The pre-cat isn't performing well... because it's not there.
Also, look at the very top of the stock header. That hole is where the stock pre-cat O2 sensor is. The location on the SC header is pretty much the same. Being super close to the combustion chamber means it reacts quicker to the actual running conditions of the engine. That's the one that is used for closed-loop fuel trim.
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