The reason why it is a mystery is not because talking about it is illegal and can get us in trouble. Many states' emissions tests (like PA) require a visual inspection of emissions related equipment, and you want to make sure Mr. Inspector does not find out about your secret (i.e. MYSTERY) mod, or he'll fail you and you'll be forced to buy two new manifolds from Ford. Also why it is a good reason to disguise MIL eliminators if you live in a visual inspection state.
