Nowhere in here does it say anything other than stock exhaust is illegal. If this were true, this would mean anyone who replaces an aged OEM muffler with a non OEM system at one of those shit exhaust shops (i.e. Mieneke or Auto Air Brake Muffler City) would be breaking the law.
316.272 Exhaust systems, prevention of noise.--
(1) Every motor vehicle shall at all times be equipped with an exhaust system in good working order and in constant operation, including muffler, manifold pipe, and tailpiping to prevent excessive or unusual noise. In no event shall an exhaust system allow noise at a level which exceeds a maximum decibel level to be established by regulation of the Department of Environmental Protection as provided in s. 403.061(13) in cooperation with the Department of Highway Safety and Motor Vehicles. No person shall use a muffler cutout, bypass or similar device upon a vehicle on a highway.
(2) The engine and power mechanism of every motor vehicle shall be so equipped and adjusted as to prevent the escape of excessive fumes or smoke.
(3) A violation of this section is a noncriminal traffic infraction, punishable as a nonmoving violation as provided in chapter 318.
This is a state statute straight from
www.flsenate.gov .