blacktop o2 sensor, redtop engine

i have searched all over and i get a different answer from each thread. im using a “fatty” o2 sensor from a '95 300zxtt on a redtop harness. the plugs connect to each other but im not sure if the wires line up. on the sensor im using middle wire is signal and outer wires are for heater. my harness wires are brown, tan, and black. my question is on the sr harness is the middle (tan) wire signal or is it the right (black) wire? today i disconnected the sensor and noticed no change at all in engine behaviour. i also tried to get a volt reading but it was all over the place. anyone know for sure? thanks