Furnace precision tune up; clean and tune up furnace; clean burners, test ignition components, adjust gas level, test safety circuit, check indoor motors, checked all electrical components, tested indoor air flow, checked heating temperatures, and tested overall furnace operation. Air Exchanger and tune up. Remove filters and core to vacuum. Also clean cabinet interior. Inspect bearings on blower assembly. Install core and filters. Clean off outside hoods. Test operation of air exchanger. Gas valve low pressure is too high and cannot adjust it due to defective gas valve. Recommend replacing gas valve. Also recommend a surge protector, blower wheel cleaning and EAC filters. Ordered filters and will follow up with customer regarding gas valve.