I recently installed an Appalachian insert and have questions about the air intakes. 2 are in the doors, and 2 are up high on the front corners. My question is where do the top ones vent? The only way I can get the fire really blazing is to crack the door, then it really dies down when I shut it. Could there be some blockage in the upper vents? I also would like to know the best settings for both vents and the damper for longer burn times.