The right HEGO signal wire is connected to pin 44 of the EEC and is Tan with Orange Stripes. The left HEGO signal wire is connected to pin 45 of the EEC and is Tan with Red stripes. For both HEGO Sensors the signal ground is the Grey with Red stripped wire.
I have a switch on my 92 that is 3 position. One position is left, one right, and in the middle position neither O2 sensor is monitored. It was installed by the previous owner and I have been told it was done by splicing in to the wires near the EEC. I do not know what he used for the gorund side nor do I know how to advise you on a 4 wire HEGO.