[rfmaster]

If you are running headers - either three wire or four wire is must. You'll need to wire a simple relay controlled circuit to turn heater when ignition is on. Heated O2 provide correct O2 concentration in exhaust gas stream faster than old style single wire O2 sensors.
Optimally, four wire heated O2 provides a ground return wire back to ECM. Exhaust system may not provide low resistance path back to ECM. To avoid ground return loops fourth wire is used. (2x heaters, Gnd return, O2 signal = AFS-74)
In three wire O2 sensor you have 2x heater, O2 signal...

//RF