Furnace clean and tune. Cycled system. Checked heat exchanger. Found minimal rust and corrosion in chambers with camera. Removed, checked, and clean burners and flame sensor. Both ok. Igniter tested ok. Checked and adjusted gas pressures to maximize efficiency. Checked and tightened electrical connections and clamps. Cleared drain line. Found some bearing wear in ventor motor. Preformed combustion test and found normal levels in exhaust. No CO found in airstream. Average life expectancy for this unit is 14 years. Some evidence of system getting worn, but system operating normal at this time. Job complete.