by expanding the ductwork i mean its like adding air pressure to a can then when the fan stops it relaxes it currently has a 1/3 hp 4Ton blower im going in the morning to try a 1/5 hp motor to see if that helps

i installed an E3EB-10H furnace in a 14'x70' mobile home and it blows way to much air through the vents is there a slower fan motor that i can get it is on the lowest speed and it still expands the ductwork