Preventative maintenence inspection on two Carrier high efficiency furnaces. Replaced both 20x25x4 air filters. Humidifier pads in new condition. Cleaned flame sensors and checked ignitors. Visual inspection of burners. Flush condensation trap and drain lines. Run test each system in both stages of heating. Both are operating properly and within specs for temperature rise, and blower and inducer motor amp draw. Pvc flue vents in good condition and no sign of leaks. 0PPM CO detected during testing. Run test humidifiers during heating operations. Sunny explained colder temperature in smaller kitchen area. Dampened down vents near thermostat and sensor to prevent short cycling, and to force more air into that area. Also adjusted continuous fan speed up to move more air during idle time, and turned Dan more to on to continuously circulate air to even out temperature between rooms.