Dick's 2002 millenia - OBD code 421
 

I have the common pre-cat issue on the left bank. The milly is a base model with 105k. Has anyone had success with using the spark plug non foulers? If so, will it pass state inspections? By that I mean will it register w/o bad codes and provide good codes to pass? Give me what you know b4 I waste my time! thanks to all of you who have experienced this issue. Also, where could I get a new one for less than 500 smackers?:(