Exhaust leak

The last item on the failed safety report was an exhaust leak, which sounded like it was coming from the engine compartment. So I checked the exhaust manifold bolts and found a few that were quite loose. I thought this must be the issue, and dutifully tighened them all. When the truck was started it sounded quieter, or so I thought, but I was going to take it back for another safety attempt anyway.