Unless you hear rattling inside the cat, it'* probably OK. Check for a exhaust leak. This includes the exhaust gaskets. If you get a can of seafoam and then suck about 1/3 of that can up threw one of the smaller vacuum lines, then shut the engine off and let it sit for about 20 minutes. Then start the engine. It will smoke a lot. Have a flashlight handy and watch real close for any leaking smoke.
The guy at midas told me to bring it in and they would do test on the cat coverter and see if it actually bad for free. But he does not recommend using seafoam, but I tend to believe you guys before him. He thinks the P0420 code is my cat converter but I will take it to him today and we will see.