If the engine is misfiring badly enough, and pouring enough unburned fuel into the cat, it can ruin it. There'* been some reports of some after-market cats setting a code for the rear O2 sensor. So, let'* focus on the misfire issue, and work on the cat later.

ok..but i just had the plugs and wires done yesterday.

With Bosch plugs, right? Sooner or later, you should get those out of your car, and put in some other brand. Get copper of iridium. How were the posts on the coils? Any rust? Make certain that none of the rear wires are touching the O2 sensor. When you replace the O2...stay away from Bosch, also. AC/Delco or Denso only.

The clean up all battery connections, under the back seat. Pay special attention to the bolt that holds the grounding strap to the floor pan. Clean that area, including the threads in the floor real well, and apply dielectric grease. Do the same for the connections under the hood.

which o2 sensor do i need to change...what i've read up, there are 2?

The front O2 sensor is the only that is usually replaced. The rear one is just for checking the condition of the cat. If you're getting a code....what is it?

the code was 420....i think

OK, that'* for the rear sensor. For now, I'd ignore that and work on the surging. Many have that code deleted from their PCM to keep it from being set after a new cat is installed.

ok..thank you so much. i will try all of this and this if that fixes it....i hope and pray..

oh and keep in mind i've already had 2 knew cats put on this year

If something was wrong on the car..that could be killing the cats. This is where a proper diagnosis comes in. Sure the cat was bad...but what caused it to go bad? Fix the bad part (which is where Archon is going) and the next cat won't go bad.