ISX 450 Intermittent Mystery Derate

[Allaroundag]

I'm sure this has been asked, but I'm new to the forum, so wanted to throw it out there. I appreciate everyone's expertise though. Thank you for what you all do and sharing your wealth of knowledge!

Here's the story:

I have a 2009 Pro Star ISX450 that I think I’ve been duped twice on now with garbage deletes and I’m not sure which direction to turn… I bought it and was told that because it was a “Canadian truck” (this is true) it didn’t have emissions (That was evidently a lie). I ran it for a few thousand miles without problems and then it gave us a shut down engine warning. It never did regen in that time, and the regen button seemed disabled. I took it to a shop who said it had been half deleted (no further explanation) and offered to do it correctly for 5k. They reflashed it, and since then the turbo oscillates when sitting at an idle and the pitch of the whistle varies. It also started to randomly die and have a power loss issue that I’ve described below. I took it back and they said the DPF didn’t get gutted, so they did that (don’t know why they didn’t double check this the first time). The dying stopped, but the power issue remained. Essentially it starts off strong and about 2 hours into the day it has no power. If it cools off for a while and then it does better, or if you put fresh fuel in it seems to come back
to life immediately as well. The coolant temp never gets of normal range (210 ish). The poor power seems to happen even when it’s nearly full on fuel too. Newish fuel filters as well and it's within normal range on the filter site glass. It just won’t build boost or much over 1500 RPM when it acts up. When it runs, it runs great though… seems to build boost and will hit 2200 ish RPM. I cleaned the MAF and EGR sensor thing (pass through tube on the drivers side) and a probe next to that on the drivers side. While that definitely helped it run even better it still has this eventual power loss issue a couple hours into the day. I am also going to watch the sensor video Rawz has and do some more cleaning of those to see if anything changes and then can start replacing them if it makes a difference. It seems electronic in nature since it starts off good and then gets worse. Yesterday my driver said it ran good and then he down shifted for a hill and it pretty much went into this limp mode and sucked the rest of the trip home. No CEL's are on when it happens either. Any advice you have would be truly appreciated, the shop that did the work just says to keep running it has hard as we can because of carbon build up. I think we've tested their theory enough and I am ready to move on. I need a reliable truck back. After reading some things on this forum I am regretting the purchase and then the followup work that was done. I wish I had discovered this site sooner.

Thanks in advance.