good luck with that $140 cat as you will most likely get the P0420 code again as aftermarket cat. won't burn clean enough to keep the light out as new cat. for the 2.3l motor is $2,000 for a california car as they are ULEV the V6 is cheeper but still lots of money...just use the fouler plug trick with the stock cat. as you will still need to the fouler trick for the aftermarket cat. also if you are from california it's illegal to put a aftermarket cat. on a 0BD2 car.