Performed the level 2 package cleaning. Furnace: Burners and flame sensor are clean. Heat exchanger looks good. Combustion readings were normal. No CO detected in the air. Heat rise was 51°. AC: No leaks detected. Electrical components tested good. Condenser coil is clean. Refrigerant charge was normal. Temp split was 18°. Customers said they had air escaping the plenum and it made the basement very cold. I caulked the gaps where I found air escaping. I told them to give us a call if it’s still an issues. All HVAC equipment is operating properly.