My truck started developing a slight exhaust leak sound a month ago. Thought it was the tell-tale beginning sound of the dreaded spitting spark plug. Replaced the plugs, sound still there, but truck needed plugs anyway. It's really noticable when it's cold....guess when metal heats up, it closes the gap. Mechanic friend tried this, put the truck in gear, hold the brake, give it gas. Said if the exhaust manifold is cracked, we'd hear it. Nothing. Neighbor crawled under the truck and said it was coming from the exhaust donut. Have any of ya'll had this problem? Those bolts are just totally rusted and I know I won't be able to tighten them. How hard is it to replace the passenger side exhaust manifold?