CM870 Boost issues

[Hemiterry]

I’ve been struggling with erratic boost issues on my 2006 International 5600i tandem dump with a 400HP CM870.I’ve replaced air intake and temperature sensors, exhaust pressure sensor, EGR temp sensor, new muffler, air filter, checked turbo actuator travel and my ECM flashed by International to my VIN. I continuously get codes for intake pressure and temperature. I finally crossed my fingers and spent $1300 on a new turbo controller and it fixed everything! I’ve never had over 32psi of boost until after I replaced the controller and got 38! For the last week the truck ran incredible and didn’t throw any codes. Unfortunately today I was pulling out unloaded onto the highway and I suddenly lost boost again and I’m right back to where I started. The turbo shoots up to about 30psi then falls almost to 0 and then slowly winds up back up to 30 but when I start up a slight hill it tops out at about 20psi. Obviously the turbo controller fixed it for a short period of time but I can’t just buy another one without knowing if or why this new one suddenly stopped working.