I have a non-cat encore that is only a few years old. This season it has been burning too hot. Damper shut, vent shut the temp gets over 700 for a long period and I cannot cool it down. But sometimes it burns fine, around 550. I think my wood may have some pine mixed in it, would this cause it to be this hot? Could I have an air leak? How do I check? I am open for suggestions.