If it's turbo charged, you really don't need a muffler as the exhaust won't be obnoxiously loud as the turbo breaks up the soundwaves nicely. For years, Mack trucks were never sold with mufflers, in fact the turbo's were stamped with 'muffling device' in the casting. I have no muffler on my Ford Diesel pickup truck either. Just a straight 5" pipe and it's turbocharged as well.