Based on your de****ion of the issues, it seems as if the restriction is not identical for each run. Can you access the trunk lines just before the towers? Otherwise, there is no way of adding restriction to slow the flow for one tower. If the system does not have any significant rise, it could easily do without the pumps and a gas blender could be utilized to dispense the beer much more successfully. Pumps were really never intended for the short run.
Scott Zuhse, Instructor
Micro Matic Dispense Institute