Thats not true either. You keep your o2 sensors, MIL's are just an inline plug that tricks your computer to think your cats are working fine. Even though there isn't any therebecause your stock o2 sensors are calibrated to work with your cat. converters, and since you wont have converters anymore, your computer will thing that there's something wrong with your car, so a check engine light will come on. you don't need o2 sensors if you don't have cats.