I have a 98 Chevy blazer with the 4.3 vortec motor in it. Anyway I was having problems with my cat. converter so thanks to living so close to GA I was able to just get it removed and that was a couple months ago and the problem stopped I noticed a small hesitation in it a day or so ago. but more importantly this popping sound coming from my muffler every so often. mostly it is just when I'm starting it up. Any one?

 

Sounds like your muffler is stopped up. That would cause it to run wierd too.
If you had a problem with your cat, it might've blown the material in the catalytic converter into your muffler.

Buy a cheap (straight through) cherry bomb and throw on it.