Completed furnace, maintenance and inspection. I cleaned flame sensor and wiped down furnace. I checked amp draws and components. I tested air pressure and temp splits. I tested gas pressure. I changed out air filter and humidifier pad. Airflow pressure is over the max rating for this system. I explained to customer what that means and the effects that it can have on the system. Heat exchanger is showing signs of wear and tear already at six years old due to high gas pressure coming through the gas valve and air pressure that is over the max rating. I tuned system to run more smoothly and avoid overheating. Air filters need changed out about every three months. Furnace is operational at departure.