I have a York Deluxe Diamond 95 that has recently started making a rattling noise that seems to be coming from the blower area. This noise started about 3 weeks ago and got progressively worse. A service technician replaced the blower motor yesterday, didn't help. Any idea what this may be. The cage seems tight to the furnace, there is no noise spinning the blower wheel by hand. The furnace is about 4 1/2 years old. The technician thinks it may be the blower wheel...thoughts?