There's still no official pump and dump group on Yobit or in any exchanges,but one groups is forming a community but they have yet to implement their system,because they have not gathered 5000 members,which is one that they are trying to accomplish ..
"official" what does that even mean?!!
first of all yobit is too small and they don't let anybody except themselves pump anything and make any profit. so forget about any trading and any possibility on there.
also you may not know this but pump and dump and in short manipulations are not exactly legal in many countries and it is against the law to do it even if it is in an unregulated market such as altcoin markets.
and besides, these are scamming methods not really a good idea to join any of them. but they go unnoticed most of the time since they get newbies only and when they lose they think it is their own fault not because of bad information.