Will an exhaust leak between...

[jimdigs]

The manifold down pipe cause loud exhaust? I have a loud exhaust and can feel air coming out on the down pipe flange. The muffler is fairly new and it sounds like its coming near the engine area. Just not that good with exhaust issues.

[Studebaker]

Maybe the cat is plugged not letting the a free flow

[WmWatt]

Use a piece of hose for a stethescope.
On cold days (mornings) you can see the condensed gases.