I have a buddy that was running a turbo on a 99 civic Si and he was having O2 sensor codes left and right so he bought these sensor divertors from Jesper ( I think that's the name of it) What they do is trick the O2 Sensor to think it is running right so the ECM will function properly. Two reasons why I won't do that is... Emissions picky techs and if something really is wrong with the engine/exhaust you'll never know.