think if its way out , as in too far for the car to self adjust, youll get a code. i changed the maf to the 3 inch one and it still didnt throw a code until i fitted the fmic. then the cooler charge required more fuel than the car could cope with, so threw a code. quickly fixed by tt injectors. i drove mine like an idiot for 2 years with no remap. when i put her on the rollers, the fuelling wasnt that far out believe it or not, according to the guy doing the mapping.