Customers home wasn’t getting to set temperature or 70 degrees was hovering around 68 and in the morning would be down to 62 degrees, furnace firing normal but cycling a lot when it would hit high limit, temperature going through vents was 145 degrees on my first temperature read, and not much air being produced from vents, pulled return filter and increase fan speed from medium low to medium high without filter and air flow was much better and temperature reading of supply duct was 120 degrees, customer will buy thinner filters for furnace which may be a little undersized for home and furnace is only 3-4 years old, let system run with no filter and fan speed increased and home reached 70 degrees at thermostat and air flow much better, system operational and working. Also gave customer estimate for duct cleaning ducts have never been cleaned.