Dave,
Sorry, I forgot to mention that I did do a by-pass of the internal temperature controller.
On the Boston Butt smoke yesterday, I put my Maverick probe in next to the permanent Auber probe and they tracked exactly, so I doubt that the plug is loose.
Also, I don't understand your comment about the wood. After 4 hours at 225 with the butt, the smoke out of the chimney was pretty much non-existent, but the wood was black not ashy. (Note that this is not unusual for my smokes, but just never really knew what the "finished" wood chunks are supposed to look like.)