Brake controller and Air shocks

[tman]

I've recently purchased a 2001 Silverado LS. Extended cab, 5.3. So far, it's nothing short of awesome.

I'm going to add a brake controller for towing. The easy connecter thing has 5 wires to splice into, but my Tekonsha Voyager has 4 wires, my question there, is what wire should be connected where?

I've also noticed a schrader valve to the right of the tag, and the markings in the black plastic trim lead me to believe someone has added this. I can trace air lines to both rear shocks. The truck rides just as nice as my Buick, so I'm not planning to change it, but I wanted to know if this was an option with the towing package.