In college, a few friends convinced me to cut the muffler off my Jeep ('79 CJ-7 with the 258 motor). They told me it would add all kinds of horsepower and sound really cool. Well, they were wrong on both counts - why I would want more horsepower on a vehicle that corners only slightly better than a covered wagon I have no idea, but I was a lot younger then. It get loud, however, loud enough to set off passing car alarms and rattle a few (already-loose) windows. I guess that was a benefit.