Hey Beli, there is a large number of tables in a tune, all with potential changes, and the number of channels that can be logged is also in the hundreds. Low side and high side fuel pressures that you show are symptoms, the causes can only be found with a complete view of the tune and the data log.
Judging from the first link you posted, fuel pressure seem to gradually drop during the pull, which looks like a fueling problem, as ideally these should be stable. Improved fueling is particularly important when you introduce forced induction into a vehicle not originally designed for it.
However, I'm just a guy, whereas Ted is a professional tuner with decades of experience, so I'd just listen to him and follow his advice (not coincidentally, he tuned my car and it runs amazingly well).
Buying an HP Tuners device (MPVI3 or
MPVI4) would allow you to produce full data logs and to view and even change the tune in the future, along with troubleshooting every potential issue. Also, If you have the automatic transmission (8L90), you most likely want to tune that as well, because that's the best way to avoid
the shudder and to make it shift better and crisper.