§ 613. Installation.

Except as provided in the following subsections (a) and (b), no person engaged in a business that involves the selling of motor vehicle exhaust systems or parts shall sell or install on a vehicle specified in Section 611 an exhaust system or part that has not been certified for that make and model vehicle under Article 11 of this title, beginning with Section 1050. The installer shall ensure that the total exhaust noise is not significantly louder than that emitted by the exhaust system originally installed by the manufacturer on the vehicle. An exhaust system shall be considered significantly louder than the original when it is obvious to a person with normal hearing that the system produces noise that stands out above that of most vehicles of the same make and model operated on the highway.

(a) Installation on Vehicles for Which System Is Not Certified. A licensed muffler certification station having sound measuring equipment may install a certified system or part on a vehicle required to have a certified replacement system even though that system or part has not been certified for the particular make and model vehicle by the manufacturer, supplier, or seller. Such installation may be made only when the licensed station measures the sound level of the exhaust system and issues a certificate in accordance with the licensed station requirements in Article 1 of this title, beginning with Section 600.

(b) Installation on Vehicles Not Requiring Certified Replacement Systems. Any person may sell or install any certified systems or parts or uncertified systems or parts on vehicles not required by Section 611 of this title to have certified systems. Such installations shall include an adequate muffler, as required by Vehicle Code Section 27150, and shall not be a modification that increases the exhaust noise emitted by the vehicle as prohibited by Vehicle Code Section 27151.