My old FSA BB died after 1500 miles and I decided to "upgrade" (or at least what I thought would be an upgrade) to a new Dura Ace 7900 BB cups with my FSA Gossamer Crank. Everything installed without a hitch and then the problem started. After everything was back together, without the chain on, I gave the crank a little spin..... it wouldn't even spin one full revolution on its own. Don't get me wrong, the bearings seem incredably smooth but it seems there is some resistance. Not knowing I thought, "maybe it just needs some break in time". Here I am 80 miles later and nothing has changed or "broken in". The bearing is way more smooth than the FSA MegaExo, but there is a noticable difference in resistance during every ride since.

Should I go back and buy lower end MegaExo BB cups that spin easy or is this not a good combo or what? I didn't expect a new Dura Ace BB to have this type of resistance.

There's a certain amount of drag with external bearings, but that seems like a lot.

Did you face the hanger tube, or at least check that the faces are flat and perpendicular to the axis?