[patrickt]

It can only be a couple of things, but fix your sticking throttle first. If the guys at the shop cleaned out the dirty air bleeds (which is the first thing any carb guy does regardless...) and they checked that the primary throttle setting and mixture screws weren't really out of kilter, then I might suspect secondaries coming in too quickly and causing a bog. Maybe the spring they put in there during the rebuild was too light. Locking the secondaries shut and taking her for a romp would tell you.