Hi. My exhaust catback was replaced recently, and I'm just now noticing black soot at a clamp site and more at a presoldered site at the middle muffler and a pipe,Starla BTW. My question is should I worry, is this to be expected or a leak. The mechanic had a little trouble hanging the front muffler, because of the bracket nor reaching, it's on a tilt, and it moves a little.

Any idea when the cat needs replacing?

Thanks Brickboard.