I replaced the factory tensioner pulley after 19 years and probably 270k miles with an Autozone pulley. That lasted 2 years and I guess about 13k. Chinese bearing. Only 1 year warranty. Napa carried two in stock, one a Gates and one Napa brand. The Gates was a pretty beefy part and said it would not fit with the factory dust shield in place, but since the bearing is sealed there's no problem. So I got that one. Not much more expensive than the AZ part (maybe $5?). Made in Canada. Anyway, here's a before video from my fan adventure:
It almost sounds diesely with all that bearing racket:
http://www.youtube.com/watch?v=XTfIVz7Rfa4
After, from a cold start:
http://www.youtube.com/watch?v=2F1VFVvtUSg
After, warmed up. Now you can hear injector noise, where you couldn't before. This is much better.
http://www.youtube.com/watch?v=3G7QVTnOVE0
Takes 5 minutes to change.