Yes, four prongs, I can see that. But which black wires should be wired to each other? I don't want to wire them up the wrong way, if there is a wrong way, and fire up the engine only to kill the sensor or some stupid shit like that. Obviously I don't know much about this, which is why I'm asking here.

My old O2 sensor is bad, right now it's in the exhaust header but disconnected (with no plug). So I can't just look at my existing sensor and figure it out. Would like to have a better gas mix without spending $80 on a new sensor...