Arrived on site to inspect whistling noise coming from boiler. Upon arrival, the boiler was not making the sound that Tom had sent videos of. The inducer fan was making a squeaking sound every couple of seconds which could be turning into the sound he has been hearing. We listened to the boiler run for about an hour with no whistling occurring. We believe the inducer fan bearings are wearing out and the motor should be replaced. There isn’t much else on the boiler that is capable of making that sound other than the inducer fan. Ordered the part from a local supply house and it should be available for pickup some time on Monday. We will be in touch to schedule a time for a return visit to put the part in. Thank you for your patience!