First, I agree with the change to Delo. Not that I am blaming Amsoil or Schaeffers or any other expensive oil, but the key is to get as close as possible to "normal" in a UOA, and for Blackstone that is dino oil and 6.5k mile samples.
Next, it's OK to use the dino oil as a flush agent. Nothing says you have to do several OCIs with dino at 6k miles each. Although somewhat of a waste fiscally, you can run three consequtive dino oil OCIs at 2k miles each, to expediate the flush process. Then, after those short flushes, run a "normal" 6.5k mile OCI and sample. Part of the concept is to allow the engine to normalize to the chemisty of the host oil, but part of the concept is also to flush out the previous oils. You can accomplish both with short OCIs. AFTER that, then do a "normal" OCI and sample.
Further, and I'm not sure about this, so take this with a grain of salt, but are the bearings in the Dmax ceramic? I had heard this from another source, but I am unable to confirm. This would change our view of the turbo issue, perhaps? I'm the first to admit that I don't know much about the VGT turbo in the Dmax (and I even drive one!).