Had an exhaust failure in a 421. Manifold pressure went to ambient.
I pulled power to idle and landed. I was lucky, it only burnt a hole in the
cowling and damaged the engine mount.
If I had continued with reduced power, the engine would have slumped and
the prop contacting the fuselage (where I was).
Other incidents include an exhaust failure upstream of the turbo charger and
near the spar resulting in loss of wing.
If you are in a turbo powered twin Cessna and MP goes to ambient, the proper
procedure is a COMPLETE SHUTDOWN.