Relationship between mpg and quiet diesel technology?

[scagmanf350]

I do a lot of personal research into increasing fuel economy in my diesel I run. I've noticed over the last few years that since mid 2003-Present there has been a steady decline in fuel mileage. Now I know some of the leading theories/reasons behind this are:
1) Diesel Particulate Filters.
2) Use of Ultra Low Sulfur Diesel.
3) Lowered Engine Displacement with a substantial increase in HP and Torque Rating.
4) Larger and multiple turbos.
5) and some others.
I was wondering if anyone realized a possible relationship between the decrease in mpg in association with newer quieter diesel engine designs. I noticed this when looking at some specs of the 6.0 and 6.4 liters vs. the old reliable 7.3 liter diesels. With every year the trucks got quieter, the mileage got poorer. I am unsure about any relationship in Chevys or Dodges but it is prevalent in the recent Fords (03-present). To my understanding in order to make the trucks quieter the manufacturer uses multi-point injectors to pump small amounts fuel in either the compression or exhaust stroke (I'm unsure/forgot what I was told/read) and this resolved some unequal pressures that existed in the cylinder thus making it quieter. However, the amount of fuel shot into the cylinder was not enough to push against the cylinder for any performance lose.
I was thinking it was all this extra fuel being used to quiet then engine that is either the cause or an additional cause that is making the mileage to decrease.
Feel free to destroy my theory or any of my info about how diesels are quieted, as I would like to hear what some of you think or if this has been discussed before? And I would like to see how far off or how dead on I might be. Look forward to your responses.