Now that you opened the door, please explain how an electronic scan tool is turning off a mechanical jerk pump cylinder by cylinder.
I am not a VP44 specialist, I do not have knowledge of the inner workings and programming of the DRBIII or the PCM, so I don't know exactly how it works, but I have used it and it does. I can speculate that the DRBIII can send a command to the PCM to momentarily "turn off" the fuel delivery every time the engine senses when the desired cylinder is supposed to get injection based on data sent to the PCM from the crank, cam, and injection pump position sensors. you can continue to turn off individual cylinders until the engine either dies or manages to run on 1. Also have done that with the DRBIII.
The in-tank is way beyond better than the cannister mounted pump. Its been proven to handle twice the HP the 2nd gens make for a lot longer than any other solution. Far from a joke when they go 400k consistently.
3rd gens (common rail) had the canister mounted pump, that proved to be problematic during the first couple of years, so the in tank pump was implemented and was enough to supply the Common Rail fuel pump. The 2nd gens did not have a canister mounted pump. It was block mounted below the fuel filter canisters and farther towards the rear.
In my paltry 3 years working in a shop where 95%+ of the work that I did was on the big three diesel pickups, I can safely say that I know what I am talking about regarding fuel supply requirements to the Dodge 98. 5 - 2002 Cummins powered pickups (and a few commuter buses). I know what works, and what does not. The in tank pump on a 2nd gen was a placating fix from DC to the high failure rate of the Carter block mounted pump. I have done enough trucks that went to the dealer repeatedly with poor engine operation, and a P0216 code, and the dealers fix was the in tank pump. The customer brings it to the shop where I worked, we installed the block mounted pump back into the system in addition to the tank pump, get the 22-25psi idle, and 17-20psi WOT no load. The P0216 code goes away, the truck runs great, and the customer is satisfied. I know this because several months later the same truck comes back for us to do other work and the fuel system is still fine.
DC's claim of flow not pressure is also incorrect. This is why Cummins never took a stance on that issue. From the Mouth of BOSCH - "The VP44 on the Dodge Cummins engine must have at all times, no less than 10psi fuel pressure with stock fuel lines. "
I have done the DC flow measuring test and have worked on trucks that the pressure dropped to >2psi, met the flow specs and still threw the P0216 code and ran like crap. Correct the fuel supply issue, and the truck runs fine, no codes.
Customer is informed that it is possible that the VP44 has suffered some damage due to the low fuel pressure, and to please bring it back if the symptoms return and we waive the diagnostic fee on the next visit.
BTW - the shop that I worked at was a BOSCH and a variety of other fuel injection manufacturers authorized warranty and rebuild center. We had a dedicated fuel shop that did nothing but rebuild, calibrate and test injection pumps, injectors, and turbos. We supplied the dealers in the area with their reman VP44s and other injection pumps.