it's still up to the states to require/enforce the epa guidelines for aftermarket motorcycle exhaust.

 

I tend to stay away from city riding where most of the problems I have had with drivers have occurred. Be it not checking mirrors or just not listening. I know from experience by working downtown that I can hear bikes coming but people just drive more aggressive. Maybe my view is skewed but I really do believe it makes a difference. I usually ride in the country and unpopulated area's due to the lack of traffic and the fact that I like riding some backwoods twisties. I'm not encouraging super loud straight pipes but I find nothing wrong with my d&d.

 

^^^ Regarding the above...

CA passed a new exhaust law that takes effect 01 JAN 2013. Here's a reference...
AMA on New California Exhaust Law - Motorcycle USA
However, CA has absolutely no idea how they will enforce it. They have NO plan in place for DMV testing or verification.

 

I've talked to some of my local PD (which have been known for writing people up for any little thing)...while I was out cruising without a muffler & just a car's tip, after the noise ordinance was in effect (like 9:30p to 6:30a). I was told as long as I wasn't going out of my way to draw attention to myself (i.e. pointless over-revving or pulling wheelies in traffic) that I was fine. Anymore, though I just run my shortened Two Bro's. Granted, that being said, one of the two I was talking to, I know has a bike himself. As a general rule, running through town, I try to keep my rev's below 4.5k. Once I am out of town though, that kinda goes out the window...unless it's a time I would expect most people to be sleeping.