I am not sure of the setup on your year Bronco, heck I am speaking of mine from memory, but in general, there should be 2 lines from the canister to the carb. One goes to the float bowl vent which is meant to collect vapors from the gas just like the line to the tank. Then there is a vacuum line that is attached to ported vacuum either at the carb or on the intake. This leads to the purge valve which decides when to release the stored HC in the canister to the engine for burning. I can't remember, tho, on yours if the purge valve is integrated with the canister or if it is separate.

If all you did was plug the line from the float bowl to the canister, and everything else is hooked up as it was, then this should not cause your problem IMO. But you could just hook that line up to your new carb, it has a nipple on the bowl vent, doesn't it?