Furnace clean and tune. Cycled system. Checked heat exchanger, ok. Ch caked and cleaned burners. Checked igniter, ok. Checked gas pressure. System was very dusty, but operating normal at this time. Did not have correct size filter to replace existing filter. Filter should be changed and changed more regularly due to high amount of dust in space. Employee stated that they have had some water leaking from roof where lineset comes in, from time to time. May want to have installers follow up to check seal on roof. Office to bill for job. Job complete.