2012 Isx15 acting stupid please help

[Mobilehomeguy]

New guy here….. here’s the rundown, I bought the truck with it running hot under a load. It is a 2012 peterbilt 386 demandated. A guy out of Bainbridge, Ga did the ecm work. The previous owners threw gobs of money at it with no luck, the previous owners had an inframe done, oem cylinder head, water pump, thermostat, oil cooler, had the egr cooler bypassed, new radiator, new CAC, new transmission. I bought the truck at a steal or so I thought. I went over the truck and found the IMAP sensor was broken where it plugs in and the fan clutch was slipping. I went ahead and replaced the fan clutch, imap sensor, baro sensor, and exhaust back pressure sensor. Drained all the coolant, new seal and thermostat, and flushed the system and topped back off. Truck has a 180* t-stat, bob tailing the truck runs between 185-195, I pull mobile homes so not real heavy but quite a bit of wind drag. With a 30k pound office unit running the south east truck will run a constant 200-210 on flat ground with the fan running 90% of the time at 10-15 pounds of boost at 68mph….. start up a hill and get over 20 psi thing heats up like crazy, it will get up to 225-230 pretty quick if you don’t baby it. I can keep the rpm’s low around 12-1300 and the engine will maintain temp around 205-215. Supposedly the truck is set to 575 which I feel is too much but I’m no expert. No coolant in oil, no cross contamination anywhere, no excess pressure or puking, no coolant loss…. Truck doesn’t want to build over 28-30psi….. best I can remember I should be seeing 36-38psi manifold pressure. I’m at a loss, is this all computer? Exhaust is cleaned and lightweight, truck seems like it’s using entirely too much fuel, what do I need to do?