Its all in what you want. I gained 10MPH and one gear up this one hill towing my boat. Doesnt sound like much of a gain but when your boat and trailer weigh 3100lbs+ fully packed and you have a 318 you need all you can get. It does get very loud in the cab when i am going up that one hill with the load. 18-20% grade at 3/4 mile. I can maintaine 55mph in 4th . I used to hear the truck down shift to 2nd and slow to 35. Just with the raven resonator i went to 45mph and 3rd. Now 55 and 4th.......Wooohooo the only down thing is that under 35mph i have a tone that is almost too loud when i am towing.