You may have but you don't want to just swap parts. That gets expensive.I seriously think that I killed the cat by driving too long with the misfire.
Get a non-contact thermometer (one of them things with a laser pointer attached) and measure the temperature going into the CAT and out of the CAT. You'll want to get onto the pipe, not in the heat shield.
The outlet should be significantly hotter than the inlet (by easily 100 degrees).
If it isn't, that CAT lost its ninth life.