Should I delete? Delete comparison

I was just talking to my guy that deleted the EGR on my 6.0 and he told me he figured a way to do the delete through the computer. Guys mail them to him, he programs them and sends them back. He said mpg increase, depending on how you drive, is around 2mpg. He also does it for big trucks,now if you can add 2 mpg on a big rig, that will add up quick. He claims that he figured out how to trick the computer so even a dealer thinks it's still stock. Maybe he's blowing smoke himself but I do trust him.