I have a Quatro true blue 90 furnace that is approx 10 years old. I kept smelling gas so i called the gas provider out they came and did leak test and found that it was all good , but they found that the smell was coming from the exhaust vent and there was black stuff in pipe . I have noticed that my heat from vents doesnt feel very war and the furnace seems to run a lot . I also have used more propane then i think i should have. Now i had HVAC guy come out and he is telling me that my heat exchanger is bad and that only 4 of my burners are lighting. He is also telling me that he cant get parts and i should just put a new furnace in. I found parts online through Texas furnace . I guess my question is does this sound right and should i fix the furnace or put new one in ? Thanks for any input.