Built in fireplace when the home was built in 1982. Corner type with the flue pipe going straight up and through the roof. 2 fresh air intakes from outside air are installed. Problem is when the blower is turned on above low speed we get a smoke odor into the room. I have had the fireplace apart for access to the damper area and found both holes for the damper rod through the flue pipe were greatly enlarged. Could not get at the back hole from the fireplace so would have to remove part of the false wall front over the fireplace for access. With a mirror and could see the enlarged hole. The blower fan draws air in at floor level and circulates it up and around the firebox and blows it out the top front of the fireplace. My question is how is the best way to fix this enlarged hole. One idea is to use a piece of sheet metal, drill the proper size hole, places fireproof insulation over the old hole and clamp the "patch" in place for proper operation of the flapper. Then do the same with the front. I did a temporary fix to the front end of the rod with furnace cement, oiling the rod first so the cement would npot stick to the rod. It help a lot but did not stop it. I am sure the smoke is being drawn from these two enlarged and open type hole that lead directly into the flue. Is my repair idea sound or someone have a better plan of attack? Any and all suggestions are appreciated.