Wow! If you can't chase a combustible gas vent properly, just cut out the TJI floor joists, a few of them, who cares. Not only that, look at the joists closely, they are homemade. Ripped 1/2" OSB with 1x2's stapled/glued to the edges. Not just one, all floor joists! Tried to save a buck or two and now we have a major structural issue. Basically, this house is unsellable as now this has to be disclosed. Sellers inspector should have caught this when the current ownwers bought the house. Some people just amaze me!