I got one of those auto meter air/fuel ration gauges and was wondering what color wire to splice into. I tried the main oxygen sensor wire but it's shielded, so I need to find the pcm lead wire. Not sure which color to splice into any suggestions?
90 305tpi

Oh and i know theres a high and low wire going to the ecm, which one do I need to splice?

 

What is it "shielded" with?

 

??? On my autometer gauge all I had were three wires. RED--> power BLACK--> ground and PURPLE--> to the O2 wire on the harness side. I just followed the directions the gauge came with.