Hello Taco! I live in the northeastern part of Georgia which is the foot hills of the Appalachian mountains. The Tacoma does a great job of towing. I try to take it easy and it seems to do just fine. Mine is equipped with a factory tow package with the transmission cooler and wiring harness for electric brakes. I bought a Prodigy II brake controller from Somebody on craigslist and bought a wiring  adapter from Camping World where it plugged into the controller and to the wiring harness on tow vehicle. Works great!  I have not had any problems with the engine over heating or braking issues. I know our mountains may not be as steep as yours but I am satisfied. I had a F-250 years ago with a diesel engine. With the high fuel prices, I had to step down for something a lot cheaper to drive. Mine is a v-6 engine with a automatic transmission and most of the time when going down hill while pulling, I shift into the lower gears and let the engine and tyranny do most of the braking. My owners manual says I can safely pull up to 6500 lbs. I think my Niagara is around 4,000.  I hope I answered your questions! If not, PM me and I will be glad to help more! FCJ