Also...just to clarify, it looks like it only came through when I had
it set on the chest level vents (not sure if there's a technical name
for them). That's where it was most obvious, at least. And it only
came in for about a minute and then stopped. I just bought this car a
month ago and it was inspected and everything. What's strange is that
the exhaust system was done, so this shouldn't be happening already.