All the VNT problems outlined above can be remedied by 3rd gear WOT to redline twice daily, similarly with clogged intakes(before they get clogged). ULSD doesn't clog intakes, but it might leave 1/8" or less, like Jason's 06 golf intake(I checked).
Not exactly with your situation.
Check those codes with VCDS and report back, sounds like you might have other issues to work out.
Also - I was exaggerating a little bit about WOT to redline, even though its pretty common for me
:lolly:
My gf's car would often go in to limp mode. I believe it was the vac line that ran to the ecu. I guess it is common for it to make the ecu think that the turbo is boosting higher than it is. Once that happened it would completely cut the nuts off of the car and you would have to downshift to third to make it up a hill on the interstate.