My Kaa-2 (Coal Only) also came with hanging baffle plate. The baffle plate blocks the gasses from going under the water wall baffles, and out the exhaust. The plate makes the gasses go up, over, and down between the water wall baffles. NO PASSAGES in the Keystoker "Stoker" boilers that I know of. You have water wall baffles. Stick your head in the ash pit, and look up. Those are water wall baffles (Baffles filled with water). Make sure you clean all around, in-between, and on top. If not, heat from the gasses will not get absorbed into the water wall baffles, due to build-up of fly ash, etc.. Your boiler will run a lot harder. Cleaning the water wall baffles made a HUGE difference in my Kaa-2 performance.
Here's what happens; You get your new boiler. It takes a winter, or two, maybe three to get're dialed in. During that time, hidden fly ash is building everywhere you can not see. You never clean it during the annual cleaning, because you can not see it. So, just when you think you have the boiler all figured out, and dialed in, you clean the water wall baffles. Now you find out the feed needs to be backed off another 2 - 4 turns. Now you have the boiler dialed in..........
My Kaa-2 struggled during the deep freeze. It held its own, but had no extra. The stoker ran continuously. After discovering, and cleaning all the build-up I couldn't see, the little Kaa-2 laughs at the deep freeze now. ........and that's with the feed backed off. So, when doing the annual cleaning, don't clean only what you can see. Clean what you can not see.