Furnace clean and tune. Cycled system. Checked heat exchanger, found some rusting and corrosion in all chambers. No visible cracks found with camera at this time. Checked, removed and cleaned burners and flame sensor. Both were very corroded and worn. Checked electrical connections and clamps. Cleared drain lines. Checked and adjusted gas pressures to maximize efficiency. Found bearings in blower motor are worn and noisy. Found indications of crack in transition assembly. Water damage found on both sides of transition assembly. Preformed combustion test and found normal levels in exhaust. No CO found in airstream. Average life expectancy for this unit is 14 years. This system is well over that age and is worn. This has led to higher utility costs and longer run time. Due to age, condition, and cost of repair, second opinion is recommended. Future failure is expected. Job complete. No charges pending results of second opinion.