serpintine belt
 

so i just replacement my belt....and i can't tell if it is just my imagination, but the vehicle drives much better. feels more responsive. could the old belt just have been too loose or am i just imagining things?

The latter

Maybe you bought one of those 10+ hp gain belts:p

I did the same thing, and a vibration I was getting occasionally under WOT has not reared its head since. I see no reason for this at all, and the vibration may show up again, but all I can figure is perhaps the old belt was removed and installed backwards. It was in good condition too, but obviously needed to be changed after 13 years. *shrug*