Cummins ISM not reading boost correctly?

[Magard]

I don't have first hand knowledge but I have read here sometimes air can get into the radiator from the turbo. It has coolant lines to it so somehow I guess it can get boost pressure in radiator. Another thing that I would suspect is turbo speed sensor. If the sensor isn't reading correctly it could make it defuel trying to slow down turbo. I know you said you have a new turbo but that doesn't seem to mean much. I just had a bad speed sensor on what I believe to be a new turbo on a cummins reman. Just throwing that out there I'm pretty new to all this emission stuff someone else can help verify that theory.