I haven't dealt with too many upper class guys, but the "bosozoku's" are usually stupid ass teenagers trying to be bad asses on 200 cc bikes with a straight pipe to make the exhaust as loud as possible. Some of the groups are a bit harder, daring the police to chase them, hitting cars with sticks/flags, blocking traffic, etc. The ones really trying to be tough ride without a helmet on, which is a big time no-no for the police here. It's really rare for them to mess with Americans with "Y-plates" though.
Funny, the way the police are trying to combat them now are to post cartoon pictures in major shopping areas depicting them as clowns riding kids bikes. This depiction, they think, brings discredit to them and their families. They hope the families will pressure their kids to knock it off. This hasn't been real effective yet...