Wow. You lucked out in the scheme of things. I had a cat do the same thing, but the smell when I turned the heat on gave me a clue. A pretty cheap fix for what it could have been. I have been researching getting my truck tuned by Justin, but am going to opt for the AutoCal for the reasons you were concerned about with the dealership. However, it gives me new confidence that they didn't mention anything to you about it.