Arrived to do a performance maintenance. Set up for combustion analysis temperature split and static pressure tests. Found that the system is operating just above the systems maximum rated static pressure. Verified operation of all mechanical and electronic components of the furnace. Checked blower for cleanliness and to see if there is any play in the bearings. Found that the furnace fan is excessively dirty considering the age of the equipment. Checked the systems ductwork and found it heavily coated in dust debris. Checked systems heat exchanger to ensure proper venting of flue gas. Verified operation of the humidifier. Spoke with homeowner about the system. With homeowners approval replaced the furnace filter and humidifier panel as well as signing up for the maintenance membership. Furnace and humidifier are operational at this time.