South Carolina Code of Laws
§ 56-5-5020. Mufflers.
Every motor vehicle shall at all times be equipped with a muffler in good working order and in constant operation to prevent excessive or unusual noise and annoying smoke and no person shall use a muffler cutout, bypass or similar device upon a motor vehicle upon a highway. The engine and power mechanism of every motor vehicle shall be so equipped and adjusted as to prevent the escape of excessive fumes and smoke.
Antique
Available for vehicles that are at least 25 years old and used in club activities, exhibits, tours, parades and similar events, but not for general transportation.
YOM
Vehicles that are at least 30 years old, driven like a regular vehicle, and do not have a gross weight of more than 11,000 lbs and an empty weight of more than 9,000 lbs are eligible to display YOM plates with DMV approval.