I don't know how it aplies to Diesels exactly but on gas engines you can add a resistor to the Mass Air Flow (MAF) sensor tricking the engine into thinking the ambient air temperature was colder then it really is, and on gas engines this cause the computer to add more fuel to compensate for the higer air density at cooler tempuratures.
Come to think of it you are most likely causing the injectors to open just a fraction of a second longer then normal which will add more fuel in general, but not in as huge of amount as replacing the injectors. This is kind of similar to the result that you achive by increasing the injector pump pressure on non-EFI engines, just like in
Lem's article shown here. This kinda intruiges me
, this is making sence from what i've learned about gas engines. If any one in here has added an aftermarket exhaust and lost any spool in their turbo due to reduced EGT's then this is a solution to add a small amount of fuel, raise the EGTs back to stock and really benefit from their new, free'er flowing exhaust.
Any chance you can get your truck to the drag strip and make a few runs. i'd like to see the numbers and compare them to others.