Performed a preferred customer furnace cleaning on the attic furnace. Cleaned the burners and the flame sensor. Checked the furnace heat exchanger. Wiped down the inside of the furnace. Checked the electrical. Cycled the furnace and performed a furnace combustion test. No issues with the furnace at this time. Basement furnace. Cycled system. Checked heat exchanger, minimal rust and corrosion. Checked and cleaned burners and flame sensor. Checked and adjusted gas pressures to maximize efficiency. Preformed combustion test. All readings were normal. No CO in airstream. Replaced filter. System operating normal at this time. Guest house furnace. Cycled system. Checked heat exchanger, ok. Checked and cleaned burners and flame sensor. Checked and adjusted gas pressures to maximize efficiency. Checked and cleared drain line. Preformed combustion test and found all levels normal. No CO in airstream. Recommend replacing filter on this unit. Job complete. Customer is interested in using MR POW