Grit Dog - I’m not going to bad mouth the garage that replaced the turbo (though wish we had tried the MAP sensor first) because I got that same advice from 3 dealership garages that looked at it over the couple years I was dealing with it. Sporatic problems are tough, especially when needing significant load to elicit. The good news here is that garage saved me significant $$$ from what the dealership garages quoted.
Since you’re in WA I will tell you that the guys that replaced the MAP sensor (directed solution from me after discussing it with my home garage) was H & H Diesel Repair in Fife, WA. I didn’t give them a real chance to diagnose etc because we were traveling and they were working me in to a full schedule. I can tell you they seemed to know what they were doing, worked with me to squeeze my repair in and tested it as best they could without dragging my 5er around. They concluded the new MAP sensor behaves a little different from the one they replaced. Couldn’t confirm that difference was related to my issue but made a good case it might be. Bottom line, I would go there again if in the area.