When my car was in Florida I rerouted the hot water line the goes through the plenum. Since I moved to Colorado and it is much colder here should I reattach the line to warm up the plenum a bit?
Correct. They are there to keep the TB from freezing up. There is NO performance gain or loss with out without them so you might as well leave them hooked up no matter where you live. That's one of those old school mods that did nothing.