You get a ticket when you modified any part of your car and make the functions of that modification different from the original intent of the manufacturer.. example would be the exhaust... the muffler was designed by the manufacturer to reduce the noise level by the design of the internal chamber to cancel out noise as it passes through. A straight through muffler which we all love is the exact opposite of that design regardless of whether their is an audible noise heard or not. I know it sucks because the law also specified a certain decibel that makes it legal... but the catch all Vehicle Code is what kills you in the end.