Unfortunately the gap with the old pump could have been terrible and with the new pump is also. At this stage of the game I would not worry about it until you verify everything is working correctly As far as the a/c you are partially correct that when it's running the Condenser gets hot and prewarms the air entering the radiator. Unfortunately even when it's not running with that thing sitting in front of the radiator like a big ole billboard The restriction is like running with your hand partially blocking your mouth/nose, much harder to breath. This is part of the reason the factory made all of these modifications on a/c cars.