86 190E 2.3L 16V, 2 95 320TE's, 02 S500
Was the OEM sensor a 4 wire? If not, then ditch the brown. Do the full tune up. Cap, rotor, wires and plugs. Get NON-RESISTOR plugs. (Denso T20EP-U) With these steps, you will at least have a base line to start from. When was the last actual tune up done on the car?