does it matter if your o2 sensor doesnt have all the exhaust go past it? ie. exhaust going out the external gate. will it think you are running lean because you dumping some exhaust out and the ecu doesnt know it. this may be a stupid question but im curious.please explain your answers

 

you would think it does, but my wideband doesnt change at all. it measures the oxygen available in the outgoing exhaust. therefore if the exhaust goin out of the dump tube has the same oxygen content, it shouldne matter.

 

Also, your ECU doesn't read the o2 sensor when at full throttle, which is the time where the most exhaust gas is exiting through the wastegate.