P0422 indicates your catalyst efficiency is low. If you had a misfire
issue, I'd primarily suspect that the converter was damaged by driving
vehicle while it was misfiring.
The converter in question is the one between the front and rear oxygen
If your car drove normally after repairs, this problem wouldn't have been
detectable by the rapair facility until the check engine lamp eventually
came on with the diagnostic trouble code. For that reason, it's doubtful
you'll receive any assistance with repairs.
If you're within the 8 year/80,000 mile warranty on the converter, you
might try taking the car to the dealer. Of course, if they see new
aftermarket wires, they'll probably figure out what happened.