I have had a hard time finding this info so I thought I'd share my experience.
Emboldened by FisherMedic and many others, two weeks ago I finished replacing my oil cooler, BPD EGR cooler, STC fitting, blue spring kit, and thermostat.
Truck started after a few minutes total crank time, had to charge once in between.
Had several issues, some I fixed quickly- forgot to plug back in the #3 injector, for example
and I had a bad EGR valve, wouldn't open, replaced.
So having taken care of all that, I still had two lingering issues.
First, Scangauge showed ICP was always too high, while IPR was almost always stuck at 14.4 except under heavy acceleration. A/E showed codes P2284, Injector Control Pressure Sensor Circuit Range / Performance, and P2288, Injector Control Pressure Too High.
I did a lot of searching and found references for ICP too low, but little to help with this code. Some said it could take 150 miles to get the air out after the STC fitting opened the high pressure oil system, but double that still didn't help. ICP Volts was pretty steady and within range, so I mostly rejected a bad sensor.
I ordered another new IPR screen kit and this weekend I finally got around to pulling the IPR to check it. DieselTechRon has a video showing how to get to it without pulling the turbo. Still a pain to get the heat shield to snap back on the IPR though. Found the new screen I had just installed was all sucked in but didn't appear to be open. Apparently I wasn't as clean as I thought I was under the oil cooler. Anyway, IPR and ICP are now behaving so I guess that was the problem, don't know if it will come back or not.
Second, before the work it had been easy to hit around 30psi boost, but now it wouldn't get over 12. It also felt weaker than before. Last weekend I tried reseating the turbo inlet to y-pipe but it didn't help. Never did hear anything that sounded like a exhaust or CAC leak. MAP, EBP and BAR were all close together at KOEO, but not identical- I didn't really expect that to be the problem, but kept it in mind just in case.
Today I removed the fitting under the EBP sensor and with a few seconds run time, found that it was passing gas well, and I had been concerned whether I'd tightened it up well enough the first time, I think it was fine. Next I checked the MAP hose, (wouldn't you know I didn't try the easiest thing first) and found the hose had a hole in it just above the intake manifold nipple. It was so close to the end that I was able to just cut the bad part and had enough left to use the hose (it's Sunday or I would have just gone to buy a new hose).
Took it for a test drive and all seems to be well. IPR and ICP are behaving normally again, and boost is back where it belongs (man these things can scat!).
So I think I am going to finally call my job a success, thanks to the help from these forums