I think I freaked a Seller off of craigslist.

[FZ6 Gotta Go!]

So have you found a bike you could see in person?

 

[pulsar2]

I've never been pulled over for my exhaust. Other stuff... In 2013 I believe the law in California changed so that all 2013 and later bikes are not legal that have an exhaust that does not bare the specific emission badge qualifying it under the CARB (California Air Resources Board) This will probably mean that there will be a change in the sound of the exhaust. I don't know anyone who has been pulled over for exhaust. My understanding is 2012 and older bikes are not under that law but I'm sure there is a law that says modifying anything that can effect emissions is not legal. That includes modifying the exhaust. Are these laws enforced? Very little or not at all as far as I've seen. The loudest bikes are the Harleys with straight pipes and no baffles or glass packing. Local ordinance for a town or city on noise may snag you.

I like how the newer BMWs and Ducatis (other's too?) have exhaust bypass valves(do they have any other name?) that open once the throttle is opened beyond a particular level. So they start off quiet and dont have too much sound while idling/low throttle setting. The valves open once you crack open the throttle,and I think they sound as loud as my exhaust. So you have a choice of loud and fast or quiet and slow.

 

[Motogiro]

I like how the newer BMWs and Ducatis (other's too?) have exhaust bypass valves(do they have any other name?) that open once the throttle is opened beyond a particular level. So they start off quiet and dont have too much sound while idling/low throttle setting. The valves open once you crack open the throttle,and I think they sound as loud as my exhaust. So you have a choice of loud and fast or quiet and slow.

Those valves have been in use on many bikes including sports bikes over the years. The design is so that there is back pressure at lower RPM and volume output of the engine. As RPM/engine volume increases the valve opens and allows more volume and scavenging for the exhaust to improve engine performance. There is usually a servo associated with the valve control that is ECU controlled.
I don't think there is any consideration in the design related to sound.