Exhausts are CARB exempt, just the noise is what they car about.
Check this link for some more info from SEMA's view.
http://www.enjoythedrive.com/content/?id=8132
In response to complaints from SEMA and aftermarket exhaust system manufacturers, the California Highway Patrol (CHP) has issued new guidelines to clarify state exhaust noise regulations for use by all interested parties. The new guidelines make clear that aftermarket exhaust modifications do not in and of themselves violate muffler noise regulations unless the modifications result in noise levels exceeding California's 95-decibel limit.
SEMA and CHP have agreed to educate police officers, consumers and the industry to ensure a clear understanding of the proper exhaust noise limits and enforcement standards. SEMA's goal is to reduce improper citations and encourage modifications that comply with the regulations. It is the responsibility of aftermarket manufacturers to design and test products to ensure they comply with the regulation. We recommend that manufacturers distribute compliance information about their products and the enclosed SEMA summaries to educate consumers about their rights and responsibilities under California's regulations. Feel free to copy and distribute the enclosed materials.
In the coming months, we will compile information on enforcement actions brought to our attention. We urge you to report to us any experiences your customers have with unfair citations. We are hopeful that the guidelines will inform police officers about proper enforcement standards and procedures; if the guidelines prove ineffective in practice, we will undertake other measurers to seek fair enforcement of the regulations.
Thank you for your attention to this matter. If you have any questions, email
stevemac@sema.org.
Contrary to some citations issued recently, exhaust modifications that increase noise are not automatically illegal in California. The regulations allow exhaust modifications increasing noise up to 95 decibels.
Everyone needs to know your rights, don't let some stereo typing police officer point you out.
Rob