Jack 6/26/2012Any type of misfire (p0305 = misfiring on cylinder 5) can ruin a catalytic converter in short time. You have codes for both cylinder banks for Converter efficiency below threshold. You need to have the vehicle properly diagnosed to see what is causing the misfiring. The misfiring has most likely ruined the converters already due to the excessive heat created in the converters from the misfiring.They may not be clogged yet , but they are most likely heat damaged, which is why you have the p0420 and p0430 codes.
RC 6/26/2012Are you saying the dealer pulled trouble codes P0420, P0430 the first time? How many miles on the car, and are you the original owner?