The cat. converter is breaking up inside. When the car idles at a stop, the converter vibrates w/ an annoying pinging sound. Other than the noise its makeing, is there anything I should be concerned about? Can it cause other problems?

 

Yes, if you are sure it is the cat, gut it or replace it.

 

A clogged cat can cause many many problems, It can get so bad that your car will hardly run at all. You'll mostly notice at first that it will lose gas mileage, and decrease in performance, or that you will have a much lower max RPM.

I'd suggest replacing it with a Catco or Carsound 3" High-flow cat. It's as close to a gutted cat that you can legally get

 

Are you sure its the cat? Because if one of the air tubes has come free, it will bang around, depend where it has come loose. I had this happen to me, but only after my new cats were installed. I thought it was the cat going bad again, but turned out that the air tube had just broken off and was hitting the cat. Just a thought.

If its the cat going bad: loss of power, cats glowing cherry red, the rattling of the catalyst inside and drop in gas milage.