Would I notice anything? If so, which one? The truck is stock and will remain so, don't want loose reliability. Any thoughts.....the truck has 40,xxx miles and runs great, gets 17mpg.

 

Prolly be better off with a Blackbear tune or something of the sort.

 

What my Diablosport Predator gave me in increased mileage isn't worth mentioning.

They're a great diagnostic tool, for adjusting parameters and reading and clearing trouble codes, but nauticastar87's right,getting a tune would be a better deal for less money.