Air fuel control derate?

[Hammerhead]

Fuel pressure and system sound stable. On to the air side...you say CAC is good so;
VG ring sticking or not full free travel?
VGT Actuator?
With insite connected is there a discrepancy between "commanded" and "actual" for VGT closing?
If your demandated, have you checked that you don't have leakage of charge air escaping from the Venturi blocking system? Perhaps this is starting to come free, occasionally releasing then vibrating closed again?
Exhaust leaks, manifold and turbo gaskets? Perhaps the drive side pressure isn't holding, EGR gas blocking plate compromised?