CapeCoaler wrote:If it is not pegging wide open it is not an issue, yet.
The extra large opening at the top may be creating some kind of funk with the draft.
It will reduce the velocity of the exiting gasses at the enlarged end, but I doubt that it would have much impact on total draft. IIRC we are talking about a 30+' chimney, it should draft well with a 3" hole in it.
eng 1 line, save that chimney sweeps number. He is an honest man. Many would have sold you a liner you did not need.