I’ve owned and operated my Mt Vernon AE stove for approximately 8 years. Besides the occasional igniter replacement and the fouling of the augar optical sensor I have had very few issues with this stove. I burn a premium brand of softwood pellet (red fir/pine) and clean the stove every 200 lbs of pellets (once a week during colder weather). This year the stove has developed a loud hum accompanied by brief vibration noise during the initial start up faze. It last for about 30-60 seconds while the combustion blower is pulling the hardest then quiets down and functions normally for the duration of the burn. I assumed it was a sign that the combustion motor bearings were showing their age and I replaced the motor and fan. To my disappointment the same noise is present with the new OEM motor and fan. I have inspected and cleaned every inch of the intake and exhaust system thinking that there might have been an obstruction blocking the free flow of air during high fire but have found nothing to substantiate that theory. I’m running my stove in automatic/softwood, flame height at -4 and deferential temp at 1.5 and convection blower on “quiet”. Anyone have any suggestions on where I should look next to solve my noise issue?