Basement furnace has slight noise from age of unit, but nothing to be caused for concern. Typical operating noise. Furnace door is missing a peg, so possible noise is coming from the door occasionally rattling. Ran the system with and without filter. Ran system with door on and off. No over amping from inducer motor or blower motor. Blower wheel is clean. Inducer does not have water backed up; no paddling. Gas valve, pressure switches, burners all operating normally.