MAP sensors on diesel do more with timing than fuel rate, if they do anything with fuel rate. Boost dictates a different timing curve from a predetermined amount.
About the only thing a MAP sensor does with fuel on a diesel of that era is cut the fuel if there is too much boost.
A diesel isn't like a gas engine, they do not run at a specific ratio. Adding the "boost dooler" would actually be better because with your tuning it doesn't matter so why have a CEL illuminate. The engine will limit fuel if boost is too low but that is to reduce black smoke and not for a specific ratio. At idle a diesel can be over 100:1 and the stoiciometric ratio is 18:1 but that produces a slightly grey haze so manufacturers don't run them that lean. Lean is okay in a diesel it just drops the EGTs. Boost is also only an indicator of resistance and not flow. Your cruise boost is a good example of that since your boost dropped but so did your EGTs, that tells me more air and less resistance. The turbo/cam I run is also a good example as my boost is lower than stock by 2-3 psi but I make 125 more rwhp at lower EGTs... More airflow with less resistance is less boost.
I do a bit of diesel tuning on the side.
Here is a good read specific to your engine.
http://www.powerstroke.org/forum/99-03-7-3l-general-discussion/238060-what-you-really-wanted-know-about-soi-7-3l-tuning-general.html
