so i bought an autometer A/F ratio gauge and have a question on the o2 signal wire where is it and what color is it. the directions say to find the signal wire and thats it. is it a wire coming off the ecu?

 

its the white wire of the primary sensor i believe, but shortband A/F gauges aren't trustworthy at all and are basically a light show. If you want an accurate readout, you're gonna need a Wideband o2 sensor, but expect to pay some $$$

 

a quality a/f gauge with a wideband o2 sensor will run you around $220-250