Furnace clean and tune. Cycled system. Checked heat exchanger. Found etching in all chambers, but no cracks found with camera. Checked, removed, and cleaned burners and flame sensor. Both ok. Found igniter getting worn with some warping found in igniter housing. Tested normal at this time. Checked and tightened electrical connections and clamps. Cleared drain line. Checked and adjusted gas pressures to maximize efficiency. Preformed combustion test and found normal levels in exhaust. No CO found in airstream. System is showing signs of getting worn, but operating normal at this time. Job complete.