I just had the cats changed on my 96SS and there were plugged as the code said they were. I am concerned that the air/fuel ratio might be off and damage the new cats over time. What is the best way to determine if the motor is running at peak efficiency? Since there are no codes being displayed at this point and the car performs fine will a dyno-tune be able to tell me if all is well with the motor. Hope someone has a suggestion...the dealer in this town is horrible. Thanks for any replies.