One thing that I've noticed after the timing belt replacement is that the engine runs better and that it seems to have a better power curve. The truck used to do a bad bearing sound or like a belt going bad, I used to think it was my alternator but I reinstalled all the belts back and same alternator and the noise is gone and now the truck runs so much better. Maybe the tensioner pulley was that bad that affected the engine performance or it might just be a mental happy feeling.