different levels of service

I was wrong many times in sample exams to select it is OK to give IPO shares to only discretionary accounts etc. Until now, I did not see any question that provides solution to be OK to treat each client differently. I am wondering if anybody came across a problem, where different levels of service satisfies broker to distribute/help clients differently. For example giving research to level 1 clients etc. Is there any possibility to distribute IPO shares differently across clients without violating CFA rules?