Furnace clean and tune. Cycled system. Checked heat exchanger. No rust or corrosion found at this time. Checked, removed, and cleaned burners and flame sensor. Both were cleaned and checked. Checked gas pressures. Checked and tightened electrical connections and clamps. All were tight and secure. Preformed combustion test. Normal levels found. No CO found in airstream. System operating normal at this time. Job complete.