For what its worth, the D turbo is capable of much more boost if you intercool the charge air. But it is very far out of its efficency map (which I have yet to see, but can tell by the temp and sound)
Heres a video of me testing with a small load. This is on diesel with the pump turned up pretty far.
http://youtu.be/ANRBPwaUxYA
Also, I did eventually melt #6 piston. I attribute it to blowby and low oil causing #6 piston to overheat and damage the rings, and overpressure the crankcase. Without doubt, this can be attributed to pushing the engine too far. I estimate roughly 20,000 miles with this kind of boost. The egt frequently was above 1200* with spikes as high as 1400*