Just pulled out my Atwood 8940 trying to find dead mouse. (2007 Grand Junction) Found a 2" hole from plenum to underbelly, but also a 4" opening from furnace to nowhere. Just hitting the side wall of compartment. Doesn't seem right to me.... Should this 4" hole be closed off? As a side note: found a dead mouse in an adjoining compartment in a hole where the toilet drain goes into tank. I think the stench was coming from return air.