I have a Yucon Big Jack with about 40' of 6' pipe. I was told that I need another device installed on the flue pipe to let more air in and this would slow the burn time down. They have to be set with a manometer and the one I have now will not let enough air in. Why will more air result in a slower burn time? There is a chance I misunderstood what I was told. So I am trying to get it right.