Just got the opportunity to contort myself under the car to try and follow my O2 sensor wires back to somewhere inside the car for attachment of "the grey wire" on my new A/F ratio gauge.

Problem is, once the wire hits the firewall, it disappears into a huge harness "rats nest" of wires, presumably one of the seemingly hundreds that go into or around the ECU. Any ideas on where I can hook up this wire that's on the interior side of the firewall?

I've checked the Haynes manual, but it says nothing, and all of those wiring circut diagrams in the back are greek to me.

Ryan