Doesn't the O2 sensor sense exhaust gas mixture and then make adjustments via the ECU? If that is the case, it doesn't matter how fast the exhaust gas is passing the sensor but rather what is in the exhaust. I have had this discussion with my former Harley riding friends. I gutted the cats and they said it would cause check engine issues and I reasoned that the sensor would have to be behind the cat to detect any exhaust gas change. I know when I removed mine from the Harley, it freed the engine up and really cooled the exhaust heat by my passengers feet where the cat was located.
The ECU makes changes +/- 10%
