It would be downstream. Instead of watching bank1/2 sensor 1 watch bank1/2 sensor 2. Sensor 1 is upstream, sensor 2 is downstream

i have the same issues. Mines happend after the Testpipe install also after it was tuned UPREV and it still got the code. The tuner suspects is a leak in the test pipe,where it meets the header. I also got the P0431 and 0420 I clear them and every 85 to 97 miles the codes come back. Mostly the P2098. any other fixes?

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After installing my z1 test pipes I get p2096 and p2098 after a few drive cycles after clearing it continuously. The O2 sensor extensions are supposed to prevent this, but that's a topic for a different thread.

I thought that the secondary O2 sensors were only there to monitor your catalytic converter efficiency, and to alert you of problems with your cat. I don't believe that it figures into AFR calculation. What's the point of checking MAFs and TBs for post-cat DTCs? Please explain to me why I'm an idiot :rofl2: