I believe if the bike is USED and has at least 7500 miles on the ODO, then you can bring in a non-CA emissions certified bike.
You may likely find that most of the late model bikes are already CARB equipped anyway (if it has a fuel vapour emissions canister behind left side-panel then it certainly has the appropriate equipment)
Some of the Touring owners may chip in but I think most of them have these, even in other States.
Incidentally there are no differences in Engine, Tune or exhaust - the only differentiator is for the Raw Fuel Emissions from the tank and as suggested, believe even that is more or less Universal at least in recent years.