Slow down there Bucky on the replacement. Are your zone valves adjustable for flow? If it has a knob (not the small bleeder) on top of the diaphragm bonnet it is probably a flow control.
Most people don't realize it but 90% of residential systems are wide open as far as flow goes. This causes the water to atomize into a mist instead of laying down a nice even stream. Depending on the head it may be adjustable for flow at the head.