Could this be a clue? When did you set in back to factory spec? And are you sure you didn't "set it back" too far?

As someone else suggested, check the diaphragm of the manifold pressure compensator and the free movement of the mechanism and also check that the stop screw hasn't come loose and wound itself out. The symptoms sound a lot like lack of fuel in the off-boost range.

Let us know what you find.
Ian