Yes, Bosozoku is young delinquent gang.
Most of the time, Bosozoku quit Bosozoku when they get 20 years old.
But now, time have changed, there're some people driving Bosozoku style car who's not Bosozoku at all or not young any more.
But before 90's or so, driving and riding Bosozoku style wasn't easy because it will end up beaten up really badly unless you are the member of Bosozoku group.
Even we had to be strong on fight those days to drive street racing style cars because these kids tried bang up street racers who is around same age with them some time.
And, there were many fights between those groups.
Time changed and Bosozoku is something not cool for youg delinquent any more.
Now, American DUB styles and VIP style (lowering lexus or Infinity sedan with big aeros and big chrome wheel) are something cool for them.
Now, most of the time, Bosozoku style is considered as "country boy".
And now young delinquent don't fight easily like before, so people who's not delinquent or bad guy can drive VIP style car or even Bosozoku style car safely.
But we still have some Bosozoku group who gangs, specially out of the Tokyo so be aware is the best even you are strong in fight

And Bosozoku group start to mixed with VIP and other cars.
They fight when they saw another "group of young people which looks easy to beat up (like few number of people)" , specialy when another group looks cooler than them or payed attention from others than them for any reason.
And some times jacks a man who don't looks strong.
It's little funny, now, there're some "middle aged people" who used to belong Bosozoku or had desire to be Bosozoku (but never involved) start driving old hilarious Bosozoku style cars and motorcycle.
They don't fight, they don't gather and drive in mid night.
They work as normal people do, on holiday they go to some meeting, like we do in Celica XX Club or Celicasupra.com, ofcourse without fight or ganging.
Difference with us is... they drive really loud reving the engine with stepping on clutch or gear in neautral!
Little hard to explain in English for me, wish I'm telling you correctly.
I'm sorry to hear you had banged from them, shame as Japanese...