Each injectors unique flow rate information has to be programmed into the ECM, or codes/CEL will result. If they replaced 7 injectors, then this process was also done. You will want to look for a record of those flow rates in the reprogram step.
If there is no record of the TSB service performed, then get the TSB and review exactly what service is performed, bring the TSB to a dealer with your truck, talk to someone who has performed the TSB on other trucks, and ask him if it has been done to yours. If it has, you pretty much have your first legal witness.
The description of this problem given by the OP, does not describe a systemic fuel injector failure. You can't "reset" damaged fuel injectors. The symptoms of bad fuel injectors are very much visual and full time power impacting.
The first thing you do with a P0087 is change the FF, a routine step regardless of other theories. And save it for future dissection depending on the outcome.
What YOU very likely have experienced is the aging fuel line collapse under suction. The lines lose stiffness with age and heat. Your July timeframe reinforces this, summer is when it will show up first, it can even disappear for the entire winter. It became a common issue with your generation of duramax, with an easy fix. Unfortunately it will usually not be something that can be duplicated in a dealer's bay, after the fuel lines cool down (and become stiffer).
Non-warranty work for stranded motorists is an unscrupulous dealer's dream come true. Any truck that intermittently shows symptoms, is always a sensor or hard part anomoly, not a systemic issue like fuel injectors.
There is a TECH BULLETIN on this specific issue, and if it was never brought to your attention, and eliminated as a cause, then you have proveable legal recourse.
This is an easy question, the way it has been presented. Justlabs is 100% correct. This discussion will be full of ignorance, but there is one and only one answer. The vehicle with the most "POWER" wins. Not only that, but torque is 100% irrelevant.
However the statement of a 1000 rpm difference is far off. The rpm difference is likely to be 4000 or more. I would not want to have to whip out the CC for the gas vehicle in this scenario. The cost per 1000ft of elevation gain will be double or triple in the gas truck.
We currently program exhaust braking (turbine restriction) into Duramax custom tuning as a free feature. It is transparent, requires no hardware and doubles grade braking force over what the allison alone provides. An additional 75-100HP to slow the train. It is especially appreciated by "rpm shy" customers with loads over 15K out west. The only time they hit the brakes is to force a downshift.