There are lots of guys here that know much more about this than I do but I will go ahead and suggest that:
- I would think the IP would be calibrated to flow the maximum burnable fuel at WOT - and this is based on the expected air flow through the engine. The throttle is a proportional control from near no-flow (idle) to maximum. turning it up will just change the slope of idle to WOT. This means you would need less pedal to flow the same fuel before you turned it up.
- unless you are making a significant change to the air flow (such as better intake, better exhaust, add a turbo) then turning up fuel won't make much difference.
- the 'turning up the fuel' will basically equate to pushing harder on the go pedal. There are probably other calibrations that could make your 'turning up' more efficient but, really (in this context), what is the difference between turning it up and taping a thin block to the go pedal (unless at WOT)?
- your truck will probably show black at WOT under load. This means you have saturated the available air so turning it up will only produce more soot.
This is my mental picture.
We will see what others think!