I had to find good speech therapy before things got better. It's still tough but it's definitely better than before. I'm also pretty social in general so that helps. I don't have great social skills but I'm polite, act self assured/not desperate, and ask things I'm genuinely interested in about other people. I thought the main benefit of a top tier MBA program is the network you build so I feel for you in your situation. Maybe you can contact the NSA or other stuttering organization and see if they can put you in contact with other MBA PWS. they are definitely out there, many working in top firms.