start up went good but

First ,Congratulations on a good break in. Have you run this carb,personal before? Check the linkage on the fast idle cam,for sticking/binding. What intake manifold,a Performer ? Performers need a thick gasket/thin steel plate adapter ,to seal a Holley flanged carb properly. That could be a cause,for a vacuum leak.Take a spray bottle of water,spray it on the baseplate area running. If idle speed drops,vacuum leak.