None.
Wyoming Statutes
§ 31-5-953. Mufflers.
(a) Every vehicle shall be equipped, maintained and operated so as to prevent excessive or unusual noise. Every motor vehicle shall at all times be equipped with a muffler or other effective noise suppressing system in good working order and in constant operation. No person shall use a muffler cut-out, bypass or similar device.
(b) 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.
(c) This section applies to motorcycles, motor-driven cycles, multipurpose vehicles and mopeds.
Custom
Available for vehicles that are at least 25 years old and of a model year after 1948, or manufactured to resemble such vehicles, that have been altered from the manufacturer's original design or have a body constructed from non-original materials. Vehicle owner has to have resided in Wyoming for at least 1 year and the vehicle may not be used for general transportation. Only required to display a single rear plate.
Pioneer
Available for individuals who have resided in Wyoming for at least 1 year and own a vehicle that is at least 25 years old and not used for general transportation. Only required to display a single rear plate.
Street Rod
Available for vehicles from 1948 and earlier, or manufactured to resemble such vehicles, which have been altered from the manufacturer's original design or have a body constructed from non-original materials. Vehicle owner has to have resided in Wyoming for at least 1 year and the vehicle may not be used for general transportation. Only required to display a single rear plate.
YOM
No law on YOM plates. Not allowed.
* Any motor vehicle which was originally manufactured without a bracket, device or other means to display and secure a front license plate may display only a single rear plate.
Definitions
Antique. Any motor vehicle which is at least twenty-five (25) years old and owned solely as a
collectors item.
Custom Vehicle. Any motor vehicle that:
(I) Is at least twenty-five (25) years old and of a model year after 1948, or was manufactured to
resemble a vehicle at least twenty-five (25) years old and of a model year after 1948; and
(II) Has been altered from the manufacturer's original design, or has a body constructed from
nonoriginal materials.
Street Rod. A motor vehicle that:
(I) Is a 1948 or older vehicle, or the vehicle was manufactured after 1948 to resemble a vehicle
manufactured before 1949; and
(II) Has been altered from the manufacturer's original design, or has a body constructed from
nonoriginal materials.