ok here is the deal i made onew of those 2 led code checher things. pluged it in turned the kay to the on position......saw the lights come on then go off. then nothing.....normally this would be a good thing.....no error codes........but i do not have my O2 sensor hooked up......shoulden't i at least get an error code for that??? i un hooked it after installing my A/F gauge......couse i wasn't getting any readings on the gauge.....hooked up the gauge only and BAM readings.......stays in the yellow at all times.....so i fugured why hook it back up......dosen't this mean my ecu is not making corrections to the injection? then why with out the o2 sensor hooked up does it seem to run better?

 

I dunno about the code checker, but hooking an A/F gauge up to the sensor wire instead on the ECU often causes that problem. It's because of the shielded cable used for the O2 sensor. Tapping into it often joins the signal wire and braid together, effectively grounding the whole circuit. Then neither the gauge or the ECU get a signal. The down side of not running with the O2 sensor connected is crap fuel consumption.