I remember one day some years ago I parked my '78 pickup around the back of a Home Depot, near a dumpster, in South Fremont. When I got back to it, and started it up, the exhaust made a huge racket. Upon investigation I found the bolts holding the exhaust system to the manifold had "loosened". I know it didn't make that racket when I parked there, so I reasoned that somebody had tried to swipe the converter while I was in the store, and either I surprised them or somebody else did and they didn't finish the job. Fortunately I was able to reattach the pipe (they had left the nuts on the ground) and get out of there OK. Some years later the truck blew a head gasket on the freeway and toasted the motor, so I wound up donating the whole thing to a charity. Probably should have kept it but I wasn't all that fond of the thing to begin with.