So I got this gauge and wire it up to one of my O2 sensor wires (prpl).

When the car runs, the gauge just flops all over the place. And when I give it gas, it takes a few moments to react.

I can't make heads or tails out of the info.

Should it be wired up to its own O2 sensor..?

 

Most like it is a narrow band A/F gauge, and it going to flop all over the place or give you a pretty light show. It will never give you any accurate info on your A/F ratio.

 

If it has a series of lights that range in color all its going to do is look pretty...to be accurate you need a wide-band with its own dedicated O2 sensor.