I got my High Flow Converter installed and it did not make the CEL go on. When you are at about 2500 RPM it kind of makes a farting sound but not all of the time. My dad thinks it could be a sound of the engine that the OEM converter muffled out. Incase it matters I have a DC Sport 4-2-1 2 piece header and a Greddy Evo catback exhaust.