Performed furnace clean and tune; inspected the exhaust and intake PVC ensuring all connections were secured, I then removed and cleaned the burners along with the flame sensor, as well as inspected the heat exchanger did find large amounts of rust did perform a powder test and did receive blowback from all 4 cells, cycled the system on and checked gas pressures, as well as performed a combustion test verifying no CO in the airstream, did ohm the igniter it did test wea, also replaced the 16x25x1 air filter. This system is currently operating normal but is showing signs of age. Second opinion scheduled with Rick 02/12/19 at 1pm Job complete