I have a Bryant evolution 355AAV furnace, about 14 months old. My PC is in my basement so I can hear the furnace when it runs. For a while (actually, probably back to last season), it used to occasionally make a clicky puttery noise. It made a lot of funny noises so I didn't worry about it. Recently this particular noise got louder so I pulled the cover, and the noise was coming from the exhaust fan. The exhaust fan assembly was mounted sort of loose (I think to absorb shock), on two screws with thick rubber pads between the unit and the furnace frame. I gave the assembly a small nudge inward and the noise went away, and stayed away (4 days now!).
I suspect what is really needed is that those 2 screws need like a 1/4 turn clockwise, and that the blower was coming a bit out of where it was supposed to be.
Anyone familiar with this design know what I'm talking about?