[TennTom]

I fired up the furnace a few days ago and noticed that the air flow diminishes the further away from the furnace. I think that is to be expected with a long run. Didn't notice the floor rising and I was walking around barefoot. For the floor to rise when the furnace kicks on can mean only one thing. Good luck finding it. I would try to see where the floor rises first when starting the furnace, that may get you closer to where the leak is.