Performed preventative maintenance for gas furnace. Inspected all the electrical components. Confirmed proper high and low voltages. Replaced the customer supplied air filter (16x25x1). Cleaned the burners, flame sensor and burner compartment. Tested the amp draw for the blower and inducer. Both are operating within the manufacturer specs. System had a temperature rise of 59°. Performed a combustion analysis on the system. System is operating at 84% efficiency with a CO level of 13ppm. Inducer port had dirt buildup inside it. This system was installed late 2019. It is a little abnormal to have this happen so soon on a newer system. As I inspected the flue piping I found oxidation buildup around the joints of the piping. Also noticed stains running down the wall where the connection to the chimney is made. This is usually signs of an issue with the chimney. This is possibly from before the chimney was repointed and a new cap installed but to be safe I do recommend having a chimney compa