CM2250 low power poor mileage

[Rockinbexpress]

Hello all, First time posting here. I have read and learned a lot but am stumped and broke. This is my desperate cry for help. I have a 2012 pete 389 cm2250 I bought a year ago the first six months it ran great and got decent mileage the last several months I've gotten terrible mileage and low power. Fixed cac leaks, 6 new injectors, and new fuel pump replaced all sensors and check valves in common rail to no avail. I've come to the conclusion it's either the turbo or a bad demandate. I am literally out of money and at my witz end. The engine was replace with a 2018 long block from cummins 100,000 miles ago and was demandated at the time of install before I bought the truck. Max boost is no more then 30 depending on temp, elevation and rpm, sometimes as low as 20-22. I bought a laptop with adapters and insite and cal and some other stuff on it I haven't hooked it up yet because I wanted to learn more about it first. I hoping I can find someone to help walk me through it and tell me what I need to look for. I'm very mechanically inclined but computers not so much and I'm afraid of messing something up but also afraid to drive it anymore but am out of money to hire this done not to mention I don't trust anyone with all the horror stories I've read. I NEED to get back to work if anyone can give me some guidance on this I would forever be in your debt. Thanks in advance