Originally posted by pimpingacura
Well you think it is the O2 sensor? Take the sensor out or just disconnect it and see if there is any difference. You should get a cell and it should run richer with no O2 sensor.
That would be true, if he were using an OEM ECU. However, the "Mugen" ECUs are race-designed and usually ignore all but the most serious codes... he may or may not get a check engine light, and his ECU may or may not run richer without it.