Completed furnace, maintenance and inspection. I cleaned flame sensor and wiped down furnace. I tested amp draws and components. I checked airflow and temp splits. I changed out air filter with customer provided air filter. With customer approval I changed out the humidifier water panel. I notified and showed customer of the dust and debris in the ductwork. Customer opted to not look into finding solutions at this time. Furnace is operating within manufacture specifications at departure.