Take a look at my thread here: http://nepacrossroads.com/about2007.html
I notice you have an older version of Keystoker like mine with the cast iron grate on the hot air output. I'm trying to do a little research on how Keystoker has changed the design of the stove internals over the years. The way mine is setup the hot gasses pass through two tubes at the top of the firebox and into a heat exchanger area, centered right behind the hot air grille. These hot gasses then pass down the sides of the stove body and down to the ashpan area. Very effective at heat output, but also very effective at filling up with fly ash. This heat exchanger area is large, flat, and difficult to clean.
Two things on my stove that I noticed when I bought it - 1) It had draft issues BAD! Lots of evidence of heat and fumes around the stoker/hopper area. 2) It was plugged solid. Under the grate was completely full of ash and coal fines, and during the moving of the stove, it was placed on it's side several times, which knocked POUNDS of ash from the upper heat exchanger area. I can't imagine how that stove burned very well.
Since rebuilding it, cleaning it out, re-sealing the grate from the rear joint all the way up to the first row of holes with fire cement, and adjusting the draft on the power vent, she's burning flawlessly.
You need at least -.02 draft to burn properly, and -0.04 is optimum if yours is not a direct vent.