C15 acert throwing codes

Hey everyone. First time poster, though I've gotten a lot of info here. Question. I have 06 w900 l c15 acert. I've having issues. I bought a pdi tuner so I could read codes because it was throwing a few. Turned out it was a bad sensor. I've always had a very slight motor vibration like I have a bad injector. I've taken it to a shop that have put it on a computer. They say everything checks out. Now on start up I run empty fine. But the first loaded load my top turbo won't spool. I only get 36 pds boost where I normally get 56. Sometimes a key cycle might fix it, sometimes it won't. It will eventually kick in. The shop says they can't do anything until I get codes and just live with it. I can't figure out whether I'm not getting enough fuel, or bad turbo, or ecm. I've seen to check turbo actuator but don't have everything to do it. Anyone have any ideas? By the way I put a pdi economy tune in it and it made vibration worse, then I put the power tune in it and thought the truck was going to fall apart it vibrated so bad. Thanks for any help

 

I have, and I don't run a tune in it now. Factory on the door is 525 hp. That's enough for me. It's only got 550k. Really don't want to ruin engine