Not trying to start an argument here, but the fueling boxes do take the VP44 out of spec by having it do something it is not designed to do--which is holding a solenoid closed for an extra amount of time. By doing this, it adds more fuel per injection stroke. It is very interesting to watch what the boxes do by using an oscilloscope. Then you can actually see how, and when, it adds the fuel.
The other boxes on the market, such as the PE-EZ and the TTPM, add fuel via the ECM. They work by just increasing the fuel quantity per injection stroke, and not actually adding another pulse of fuel
after the intial injection stroke. By doing this, they keep everything within the limits of the VP44, and don't cause any additional strain on the internal parts of the pump.
Te injection pump on my '98. 5 went out due to the fact it was one of the ones thatmissed the de-burring process at the Bosch plant. Fuel pressure was good, no boxes were installed--it just crapped out because ofpremature internal wear, something I had no control over. It was covered under warranty at 60K.
Rob, the fact that you and Mike's pumps have withstood the effects of the boxes, simply proves that some pumps are stronger than others. Look at how well John's has done. He had negative fuel pressure for who knows how long... If you look at the pumps that have gone bad, you will find that most have been on '98. 5-'99 trucks. Rarely do they go out on the newer trucks, even when fueling boxes are attached. Fuel pressure is the root of the problem for most VP44 failures, as the pump uses diesel fuel for lubrication and cooling. It is very important that anytone with a fueling box--or planning on buying one--get their fuel pressure tested prior to installing it. Otherwise, it could cost them an injection pump.
If it were true the boxes did not cause any additional strain on the VP44, why have so many failed less than 30 minutes after installing a box? I would consider this: They use so much fuel, it drops the supply pressure, and there isn't adequate fuel for lubrication and cooling. I would call that addition strain, wouldn't you? Compare it to running an engine with little or no coolant flow. If you have a bad water pump, what happens? Your engine gets hot, and will ultimately fail if kept running in that condition. Same thing with a VP44, except you don't know until it is too late--hence the reason for fuel pressure testing.
Bottom line is be smart when you BOMB a truck, and do the necessary things to ensure what you add on won't cause problems.
Attention: TDR Forum Junkies 
My truck is just stock anyway. . 
and I am happy with it.
