I arrived to inspect the complete duct system. I found the 3.5 ton system to be running on 1.5 ton of return inlet air. I also found duct work to be taped off the top of the supply plenum not allowing the system to build up the proper static pressure the system needs. I showed all my findings to the homeowner and explained that with the system installed the way it is the only way to correct it is to change the position of the system and set the ducts correctly on the plenum and to rerun the duct to all rooms. We decided to replace the return duct to get the proper amount of air to the system to feed the supply duct. The supply duct is incorrect as well. We decided to increased the return duct for now and see how the system operates with the improved return duct. Will need 3 bags of 16†duct 2 16†stick taps and 2 16†finger savor taps.