some FYI:

Q9: What is the exhaust noise test specified in 13 CCR? Can this be used for enforcement?

Sections 1030-1036, 13 CCR, were intended to be used by Licensed Muffler Certification Stations as a means of determining if an exhaust system met the requirements of the Muffler Certification Program (when those programs were operational). They specify testing procedures for motor vehicle exhaust noise alone (as opposed to total vehicle noise). This procedure specifies a limit of 95 dB(A) measured 20 inches from the exhaust pipe outlet with the engine operating in neutral, typically at a speed of 3000-5000 rpm. (For comparison, a modern rotary lawn mower with a 5-horsepower Briggs & Stratton engine typically emits approximately 93 dB(A) at the same distance at full speed under no load.) It applies only to passenger vehicles. It does not apply to motorcycles or to vehicles over 6000 pounds gross weight.

Q14: What type of enforcement action should be taken against vehicles emitting excessive noise?

Providing none of the disqualifying conditions listed in Section 40610(b) are present, the use of the CHP 281, "Notice to Correct," or checking the Dismissable Violation "Yes" box on the CHP 215, "Notice to Appear (Arrest Citation)," would be appropriate for these violations

it's all here:

http://www.enjoythedrive.com/content/?id=8132
http://www.enjoythedrive.com/content/?id=8133
http://www.enjoythedrive.com/content/?id=8135
http://www.enjoythedrive.com/content/?id=8134

...just in case