Not going to quote your previous post, but will try and answer some of your questions. First off, several of those NA wires are optional, such as truck/hatch release and dome light supervision. Some of them however will not be needed as well.
Your main ignition wires can be accessed right up the steering column. All your heavy gauge wires should be able to be caught there.
Ignition #1/#2 are NOT the same as starter wires. Ignition wires will be HOT with the key in the run AND starting position. Accessory wires are only HOT with the key in the run position and dead in the starting position. Yes, you will need your accessory wire. As far as key sense, I can't think of a single instance where I hooked it up.
Tach: This wire is what monitors the vehicles engine while remote starting and keeps the engine from keeping the starter engaged. However, with that said, many of the newer systems have incorporated voltage sensing that you don't really need to hook it up. My recommendation. Try doing without at first, and if you are having issues with the starter disengaging once the engine starts, then hook the tach wire up.
Brake wire is very much needed. It's what keeps somebody from driving away in your car when it's remote started. If it's remote started and you tap the brake, it will kill the engine.
You should be able to ignore any transponder wires.
I'm going to PM you my direct email address in case you have any questions while you're installing. I don't always have a chance to check this site, and email goes directly to my phone.
2003 Matrix Xrs Automatic