I talked to 2 mechanics about the chip, and they both thought that it was not worth the money (close to $500 for the Diablo, I believe). The reasoning was that the truck is geared up by Ford to run at a certain level, and the chip basically just made the fuel mixture richer. Thus, better output, but more wear & tear on the engine in the long run.
u-baddog: I've had nightmares about filling my new toy up with gasoline. I'm gonna put a label on the gascap (dieselcap?) that says "DIESEL!". I actually know a guy who filled up his car with diesel and drove about 15 yards before it seized up. No, I have no idea how in the hell he managed to mistake the diesel pump for gas.
Never heard about running on ATF fluid, but I have heard that you can make biodiesel out of McDonald's leftover frying oil.