This is a common issue we see these days with OBDII cars and aftermarket exhaust systems. Some systems are very finicky about properly sensing the airflow going through the exhaust system, that if they sense too much air at the downstream oxygen sensor, it will trigger a check engine light. This can be caused with a larger diameter exhaust, high flow catalytic converter, or a catalytic converter delete exhaust. This miata came in due to this issue after the owner …

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