Minn. Stat. § 169.69: MUFFLER.

Every motor vehicle shall at all times be equipped with a muffler in good working order which blends the exhaust noise into the overall vehicle noise and is in constant operation to prevent excessive or unusual noise, and no person shall use a muffler cutout, bypass, or similar device upon a motor vehicle on a street or highway. The exhaust system shall not emit or produce a sharp popping or crackling sound. Every motor vehicle shall at all times be equipped with such parts and equipment so arranged and kept in such state of repair as to prevent carbon monoxide gas from entering the interior of the vehicle.

No person shall have for sale, sell or offer for sale or use on any motor vehicle any muffler that fails to comply with the specifications as required by the commissioner of public safety.