It can be done, But I would never do it myself. WHY? well I am a diehard programmer, I do not like any form of trick boxes that go inline, and trick the stock computer into making low quality power. If you look at the Duramax computer LB7 or LLY they are quite complex, and rely on many sensor readings, and inputs from body control module, Transmission Control Module etc.
With programs such as EFIlive you are able to adjust almost anything. For instance I can make a DMAX shift better then any trick box, such as edge, etc.
why? because they dont adjust enough parameters to make it work properly.
the computer does not like changes in one area without changing maybe one to three more in other areas. you can make as much hp as you want with EFIlive, the only limiting factor is your engine,transmission, drivetrain. if you dont like programming, then get the PPE handheld programer, it puts out alot more power then most. In my trials of various products the majority of chips, programmers suck and don't compare to the good ones, you get what you pay for.
I have yet to have a customer go back to a trick box or chip.