hey guys, a friend of mine has a f-350 dually. he was traveling down the freeway the other day on cruise control, and all of a sudden the engine started popping. he said it sounded like somebody was firing an ak-47. then he slowed her down and fell in behind a big rig and it stopped doing it. it hasnt acted up since. was wondering if this is a common problem or not. im not sure about it being a cummins man. any clues as to whats going on? thanx