How do you know that no dpf regeneration is going on?
I bet it is... your model can with the torque app read out the dpf temperature.
Or egr shutoff and throtle restriction
Try it
Also if regeneration is going on and your idling the regeneration is halted after a certain time idling activating again after some rpm/load
If there was overfueling at idle there would be higher rpm.... diesel engines
have massive air fuel ratios