well, because I am a turbocharger rebuilder, it's always the turbocharger. The problem, as I see it, is that the turbo is going to be worn at that mileage. Turbos are like brakepads-they wear and need to be serviced at about 30,000 miles. They will hang on until 130,000 or more, but if we get a turbo in the shop, it allways shows wear.
I think it's important to rule out any electrical or sensor problem, and I wish some mechanics would chime in, because a turbo, with this kind of mileage, will be in need of service, but without a bigger picture diagnosis, we can't say that the turbo is the source of the problem.