Is it time to "chip" the V-10 in an E-450 class C?

Just not going to help a stock gas engine to tune it.

The shift tweaking from tow/haul lets the engine run longer in its power sweet spot during acceleration instead of trying to get into overdrive as fast as possible then lugging as you finish gaining speed. Gas engines need RPM to make the most power.

Planning so you reduce unneeded driving and modest speeds are much more effective at saving fuel than any tweaking you might do.