The 2 black cylinders (1 is harder to see, but it's there) are the volatile vapor collection system. It has no effect on the bikes performance. It may give you a slight increase in gas milage because you get to burn the gas that would otherwise go floating off down the vent lines as vapor on warm west coast days.
As for the buzz, take it back to the dealer and complain a lot untill they work on it. It could be that they did something wrong during the dealer assembly. I have an America that doesn't do that, but those are geared differently and have different handlebars, wheels and seat.
To narrow it down a bit, try running it up to 45 - 50 in fourth gear and see if the buzz starts earlier on. If not, a tight chain adjustment or something in the rims is likely. If it does, carb balance and engine mounts should be checked.
Or, it may just be begging you to spring for some aftermarket pipes that are less stealthy than stock.
