I have an intertherm 1175 gas furnace to which I recently added (aug 2002) a package air central air system to. The furnace seems to be runnnning fine but my problem is that the air that comes out of the registers is lukewarm, almost cool. when the furnace kicks on it feels like it causes a draft in the living room. we have all new windows and have even put plastic over them to try and find the draft. any ideas as to what could be wrong with the furnace or what my problem might be??