I've got the 90 FSM and it shows the X13 circuit being a common ground for all of the speakers. Unfortunately, I can't seem to find that wire in the stereo area on my car. It had a fancy stereo in it when I got it and it didn't work. I would like a few tunes even if just AM/FM for SDAC. Does anyone have the diagram for 89? It really doesn't look like that wire came in the bundle of my 89 so I'm wondering if there was a change in the connector for 90.