Anyone installed the rear fog light as a brake light on a roadster?

[Lee123]

I've got a 2010 Roadster. I installed a rear fog light and I'm trying to wire it up to come on with the brake lights or, is that's impossible, to just come on with the tail lights. When I put the fog light in yesterday I plugged it into the unused plug next to it with the orange and black wires. The wire from that plug disappears up behind the bumper a few inches to the right of the fog light. Today I pulled the big plastic panel out of the back of the trunk, but since all the wires behind it are bundled and taped I have no idea which bundle contains the wires coming up from the fog light and where I can find the green wire that I need to tap for the brake lights. I already broke the plastic base for the emergency trunk release handle while I was trying to get the plastic panel out and I'm not anxious to start randomly slicing wire bundles hoping to find the right wires. I guess it all comes down to two questions:

1. Where can I find the correct wire bundles to slice open to find the orange and black wires from the fog light and the green wire going to the brake lights?

2. Are the loose ends of the orange and back wires connected to anything? I believe I read in one of the previous posts that those wires run up to the front of the car and aren't connected, but I don't want to damage anything that might be connected to them.

Thanks for your time.