I have a question regarding a loud boom noise my furnace makes sometimes before it starts up. recently my flame ignitor went out (on a sunday) luckily i found a guy that was able to sell me a new one, well he told me it would work and it was a universal one. i had to splice the wires and remove the old connector from the fried ignitor to put on the new one because it didn't have one, well anyway i explained to the guy that my furnace has the ignitor and flame sensor all in one, he told me he never heard of that and that this one will work, well to make a long story short after installing this new flame ignitor my furnace sometimes makes this loud boom noise that it never did before, could this have any thing to do with the new ignitor and if so is it dangerous? i noticed when i take the cover off the furnace it doesn't do it, only when the cover is on from what i can tell.... not a 100% sure though because it does makes this BOOM noise intermittenly. also i can smell a silght burnt smell kinda like the smell of burnt dust? i checked inside the furnace for any signs of burning and nothing. also i noticed on the heat exchangers there looks to be a cover on the face of the exchangers that is bolted on and it has a small crack, would this have anything to do with it? it just looks like a cover though and not a crack in the exchanger. any suggestions would be greatly appreciated! also the new flame ignitor came with a list of different models it was compatible with and mine was not on it also my flame ignitor was a different shape then the one this "so called tech" sold me. my furnace is a ruud natural gas about 6 years old. sorry about the long post!....