(a) Exhaust System. An “exhaust system” consists of all pipes, converters, and chambers through which the exhaust gas flows from the engine exhaust manifold outlet flange to the end of the tailpipe.

(b) Maximum RPM. “Maximum rpm” for 1972 and later year model vehicles is the highest governed engine speed or, if ungoverned, the rpm at maximum engine net horsepower as determined by the engine manufacturer in accordance with SAE Standard J245 in the 1971, or any later, edition of the SAE Handbook. For earlier year models, “maximum rpm” is the highest governed engine speed or, if ungoverned, the rpm at maximum engine net or gross horsepower as specified by the vehicle manufacturer.

(c) Approved Laboratory. An “approved laboratory” has facilities and equipment for testing sound measuring equipment to American National Standards Institute Standard S1.4-1971.