Yeah man!! That is a good demonstration of why it is so important not to let fly ash collect on the interior walls of your fire box, baffles and fire brick. Ash will cut down on heat transfer big time!
I'm pretty anal about keeping all that stuff clean in an attempt to keep the best heat transfer that I can. I use a wire brush at every shake and load to keep the water coils clean and also run it across parts of the fire box wall. Nothin too enduring, just a minute or so of scouring..