Hoe can I tell if my catalytic converter is working properly?

What is your question?

I recently had 2 cylinder misfires that killed my catalytic converter. I replaced the coils and plugs for the the misfires and the converter, but its still running very rough. Its a lot louder than it was before. I was driving, gave it some gas to accelerate from 40 to 50 mph, the RPM's spiked and the check engine light came on and flashed. I pulled over and turned around cause I was only 5-6 miles from home. After 2 minutes the light went off. What else could it be?