Most new diesels are 4" stock too. My DMax was. And it's not a matter of needing to modify it.
I pulled my 34 ft toyhauler with my D Max no problem at all stock. I never NEEDED to modify it, but adding an exhaust helped for towing. More is always better.
I have yet to meet a guy to this day that said they didn't want more power regardlesss if thay had a Ford, Chevy, or Dodge.