Visit the California Air Resources Board Aftermarket Parts Search webpage and search the CARB number that is on the cold air intake you installed on your Ford Mustang. It will probably indicate that it belongs to a Ford Mustang of a different engine size or vehicle model year. The CARB number on any aftermarket part you use on your Ford Mustang has to exactly match your Ford Mustang's year and engine size. The part simply fitting on your Mustang's engine does not make it smog check legal; California law. It might pass another State's emission inspection, but California is quite a bit stricter when it comes to the smog check; and since the start of the STAR smog check program, where a station can lose their STAR certification if they don't inspect OE (executive order) number, they are very cautious to make sure all aftermarket parts are legal and for the vehicle being emission tested.
