94 Mazda 626...troubles hooking up my Kenwood HU

I have a Kenwood deck that I would like to put in this car. I took out the stock stereo and bought a wiring harness. Now it hooks up the two white click in connectors and the big antenna wire fine. But 2 wires are left. A smaller antenna look a like and a black small click in that says "Amp" on a little door that comes out(this wire also clicks in the back of the stereo). When I take only that wire out of the stock stereo, the stereo won't work so I'm guessing that's ground? Now if I open that little amp door and try to connect my black ground wire from the kenwood to a metal piece there, and hook hook up the rest of the wiring my kenwood still doesn't work. I also tired to ground it to the chassis...everything..aagghhh. It was so simple on my Chrysler...this is damn complicated!!!

Are there any wiring diagrams for the stock stereo that state which wire does what? Or can anyone offer their advice here?