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Old 12-28-2017, 05:27 PM   #3
JerTM

 
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Drives: 2011 2SS/RS M6
Join Date: Oct 2015
Location: Utah
Posts: 1,940
Those dtcs are likely a result of your exhaust modifications. A delayed response from rich to lean on both downstream o2 sensors. How long has it been tuned? To me it suggests the ECM is seeing a rich condition post cat for longer than it wants, suggesting the cats are losing efficiency (for stock cats). Your tuner should have shut these codes out.
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