1998 Ply Voy 3.3

I have to replace my connector pipe between 2 manifolds. Expensive. A mechanic suggested this may have been caused by the catalyic convertor getting plugged, and not letting the exhaust through the pipes as quick as it should. Does this make sense. There was some dimpling on the "middle" muffler, and this is apparently a sign of heat not flowing properly. Thank you for your reply. Pete