2003 expedition stereo

I recently installed a pioneer head unit in my SUV, and the wiring harness was a major headache to find. I have a 2 plug factory harness, and a 1 plug aftermarket.(I guess this is the only harness they make, tried them all). I can not get the rear speakers to work, any suggestions? Also installed an amp, and was thinking about just going back to my factory unit and just running everything off of the old unit.  Anyone have a wiring diagram for this, I found a power for the amp, but it powers the amp constantly, will not shut down after the truck is off. Any help would be appr. Thanks guys.

There is an aftermarket harness that has both plugs.  The second plug has your remote turn-on wire.  You can find these harnesses at most Best Buys and Circuit Cities.  Enform them that your system is amplified.Do it right the first time