Lucky here in California they don't emission test bikes yet. As for the dealers here, as of January 1st, 2013, they can't sell or install after market exhaust any longer. As of yet, we in California do not have to rebuild engines at a specified mileage. But, if your vehicle won't pass emissions testing, you have to spend up to the limit to get it to pass.
As for testing bikes, if they decide to I will register mine to my Arizona house and fix them. But if stopped, the California vehicle code states you have ten days after taking up residency in California to register your vehicle here. Having your vehicle registered out of state can be a problem if you start getting stopped a lot,,,.
As for loud exhaust, if you are not a 1%er and don't take up an attitude with the cop stopping you, most won't cite for loud exhaust. Most cops here ride bikes also.