The bike had the kit installed when I bought it at the end of June. The buzzing started somewhere around 1200 miles. I replaced the Kawasaki foam with my own slightly thicker foam. That got rid of the major buzzing.
Like I say, there's lighter buzzing elsewhere. I know I can stop it, I really haven't got the time to spare for a trip to the dealer. Just need an hour of uninterupted time this weekend, probably more, I still have the handguards to fit