The turbo cuts out after driving downhill. It resets after engine stopped.

What is your question?

When cruising downhill against compression (not using accelerator) there is a total loss of power when accelerating again. When I turn off the ignition, the turbo "resets" and functions normally until I hit the next downhill. This is for an ML 320 CDi, not Bluetec but the diesels do not feature amongst your options.