I have a Lionel M1a TMCC engine and the smoke comes out in a thin stream. Sometimes it just "pools" in the top of the stack unless I use a toothpick to insert in the stack then it comes out in a stream again. Before I take it apart, I was wondering if this could be caused by the batting covering part of the air hole? Unit seems to work OK other than that. If that is the problem, I can fix that.