Fuel
 

Does straight piping the 6.0 hurt or help fuel mileage

For some it helps, for most it hurts...yes, getting the restriction out of the system improves flow and can give you a couple extra MPG, but for the most part people find that they lose a couple MPG just because they can't keep their foot off the skinny pedal. :D Sometimes I find myself rolling down both passenger windows just to hear her spool up. The PowerMax is an even more wicked howl. A buddy of mine perfectly described what it sounds like when I start the truck "crank crank, diesel diesel diesel TUUUUURBOOOOOO"