how would an engine run if it has a bad oxygen sensor

[TurboLegacy]

my engine lags after a semi-hard run, it is sometimes hard to keep moving. i think it is running lean. i checked the plugs and they are clean. When i step on the gas the rpms dont go up, instead they go down. could this be the injectors or a problem with the O2 sensor? this problem only started after i had my bypass venting to the atmos. because it was venting, it caused it to run rich, what would have been messed up by the richness?

[vrg3]

First question - did you reset the ECU after fixing the bypass valve? You should, to clear the fuel trims.

Running too rich can foul up the oxygen sensor.

You might want to try just unplugging your oxygen sensor, resetting the ECU, and seeing how it runs without the sensor.

[TurboLegacy]

how do i reset the ecu in my car. do i do this with a scan tool?, if not where, and how much? thanks

[THAWA]

pull the batt for 30mins+

[vrg3]

I just disconnect the negative battery terminal and press the brake pedal for 30 seconds. It's never failed for me on a Legacy turbo.