Hey there, This past summer the catalytic converter 1st stage fell apart and plugged the 2nd stage section on my 2002 GTP which prompted me in deleting the cat. Prior to the cat failure the car ran good with decent mileage (approx 25 mpg). Since then I have changed the plugs out for Autolite copper 606's side gapped to 0.050" as well as NGK oem replacement wires. Now under the same driving conditions of 50/50 highway & city I am only getting 17 mpg. My question is if I need to run an O2 emulator in order to improve the mileage. My scan tool shows that the Catalyst Efficiency code comes in repeatedly every 100 miles approximately. Anyone out there experience these symptoms?? Any feedback is much appreciated,
Thanks in advance, Jeremy