I removed the plate before installing the insert. Now that you mention it, I haven't seen the secondary burn since it became difficult to burn. I remember one morning I went to light a fire and the air control lever was stuck. I had to put a good deal of pressure on it to get it to break free. Not sure if something got down the intake tube to the mechanism that closes off the air.That doesn't sound right at all. You should be able to turn down the air quite a bit if not all the way after 10-20 minutes. I am wondering if the house air plate was removed and if it is starving for combustion air. Are you seeing good secondary burn? Which model stove is this?