I experienced it once on an old Dakota that I had. Suspected the cat was bad after I had a valve job done. While it was running I smacked the cat with a hammer to break up the junk, and it clogged so bad that it killed the engine. But it has a very distinct sound. Since it passed emissions not 15 minutes before it died on me, I'm inclined to think it is ok, but I haven't had it running long enough to make that determination.

Looking up some parts just a new cam is $264 shipped from mitsubishiparts.net. Yikes. I'd be better off getting a Clearwater head in that case. Unless someone knows of or has a driver side intake cam they are willing to part with.