Customer complaint of air coming from supply plenum. Upon arrival customer showed me where unit is and the concern he has due to selling the property. Upon inspection found no leaks or breaks in the supply plenum. Went into attic and found no leaks or breaks in the plenum where the flux duct connects. Turned indoor fan on and noticed a Cobb Webb moving by the supply plenum. Air handler is vertical on a stand that draws the return air through the door. Inspected again while unit was running saw no loss in air flow or air escaping the plenum. Found nothing wrong with plenum or duct work. System is working to factory standard