Scangauge's website will have the right codes to add in. Do you have the right scangauge? There is a 'D' model for pushers, uses a different language than the one for cars & trucks.
ScanGauge - Trip Computer + Digitial Gauges + ScanTools
Can't seem to get my head around the turbo question - if it's not working, you are not going anywhere. The scangauge should help you with boost and exhaust back pressure readings, although with a 2001 the sensors might not be that extensive. If you don't have a thermocouple or a pressure gauge already in place, the scangauge won't give you a number.