External-bearing BBs like the FSA MegaExo tend to have "seal drag" when new. Give it a couple hundred miles and see if it loosens up.
The user reviews on the web don't exactly shower praise on the FSA MegaExo BBs though. I would suggest that if the FSA MegaExo BB starts to crap out on you after a few hundred miles, replace it with a Chris King BB (they have one that is compatible with FSA MegaExo cranks).