None.
Hawaii Revised Statutes
§ 291-24.5. Motor vehicle muffler.
(a) No person shall use on a public highway, sell, alter or install a muffler which will noticeably increase the noise emitted by a motor vehicle above that emitted by the vehicle as equipped from the factory.
(b) Any violation of this section shall constitute a violation and shall be enforceable by police officers. The fine for this violation shall be not less than $25 nor more than $250 for each separate offense. Any person who violates the provisions of this section may be issued a summons or citation for such violation.
Antique
Available for vehicles that are at least 35 years old, of the original factory specifications, or restored to the original specifications, in unaltered or unreconstructed condition, and operated or moved over the highway primarily for the purpose of historical exhibition or other similar purposes.
YOM
No law on YOM plates. Not allowed.