Those gauges are worthless cuz 99% of the factory O2 sensors are narrowband (0-1 volt) You need a wideband (0-5 volts) signal to be able to actually monitor whats going on. A narrowband signal will only tell you if the air fuel ratio is lean, correct or rich. By lean or rich I mean leaner or richer than it should be, even if its only .1 more than it should be. Just stop being cheap and buy a wideband O2 sensor if you really care. I got my PLX-M300 for $313 shipped from www.streetrays.com