when I connected the power under the spare tire I didnt use a voltometer.
I used a lightbulb connected to two wires to find the connections.
I assumed everything in that green box was putting out 12v?
I just connected it to an empty slot.
The power kit is rated 350Watt. I got them from walmart.

*the guy who connected my sub with the power end going to the sub said the connector was too big but he said he could make it touch. maybe that is the problem? I would have to cut the wire and add a smaller connector to it so it fits perfectly to the sub.*

I connected the factory harness to the connections (as labeled on the homepage) going into the factory amp. Pins 7 and 14 I believe.