Diesel engines are like an old hurricane lamp. turn the flame up, it uses more fuel, and the wick won't last as long.
I have a Banks kit on my 350 horse ISC. with intake and exhaust kits and a programer, we can run 33 pounds of boost and 1350 degrees exhaust temps. (max) do I care if I'm only going to get 500,000 ,miles out of it? (nope) the program in it gives us about 9-11 miles per gallon, (freeway) it will probably take 3,000,000 miles of fuel savings to pay for the Banks stuff, but Oh Well? it was on it when we got it, and I'm not going to remove it.
Did I tell ya? I can top a five mile 6% grade at 55?