Have you used a chimney brush on it lately. They get full of soot and creosote. That can cause draw problems and sounds like it might be your problem. Clean them often, and you don't have to worry about a huge build up later on. It also helps them to draw much better.So I thought the flue was the adjustment on the chimney itself to adjust exhaust side…. I do not have that I only have an air intake adjustment. I believe my terminology is as lacking as my stove skills at this point.