I have a free standing Castile that seems to be burning lazy. Feed is set correctly, and stove pushes out the heat. But it is not burning the pellets like it should. Lately I have to clean it more often and there is a lot of partially burnt pellets. I figure it is combustion air issue, but I can not find anything on where the stove draws air in, besides a bad picture of an OAK. I don't have an outside air kit installed. And can't tell where I should be looking to see if the intake side is dirty.