anyone hook up a A/F ratio gauge

just like the title says, anyone ever hook up a a/f gauge on a 94 or 95 mustang. which wire is the sending wire. theres four wires.

I'm gonna go out and look at it now, was just wanting a little heads up.

also, should I tie into the wires the sensor is attatched too, the wires that are on the extenders or the wires that are already on the car?

thanks for the help.