Well it's not ideal, but you can still get some use out of it. Since the gauge was free, just pick up an aftermarket O2 sensor and install it. You will probably want a heated sensor, especially if you have headers. But what I would recommend for tuning purposes is use a digital voltmeter and read the sensor directly. The digital meter will be easier to read than the LED gauge because it will be averaging the signal and the response is a little bit slower. You want around .45V for light throttle cruising. And up around .65V for WOT acceleration.superdart said
