factory installed.
Notice there isnt a max Decible limit in that law. If the factory exhaust in its loudest setting is say 98db. from reading the law it would seem that if you installed headers and a full exhaust but stayed at or bellow that it would be legal. 99 db and its not.
when a factory honda is 30db and silent its very easy to go over that with a modification.
BUT say the db on that ZL1 is 98 db, damn loud, it might not get an exhaust ticket if the cop is smart and doesnt want to chance it on being factory… there are plenty of disturbance laws I am willing to bet DO have a DB limit to hit him with.