Kia Rio: Excessive Soot & DPF Overload (1.4 CRDi)

Hello everyone,

I'm experiencing a persistent problem with excessive soot buildup in my Kia Rio IV 1.4 CRDi (year 2017, engine D4FC, wastegate turbocharger) and I'm hoping to benefit from your experiences.

The problem.
The amount of soot in the DPF, as calculated by the control unit, increases rapidly (e.g., an increase from just under 2 grams to approximately 13 grams within only 25-30 minutes of driving). As a result, the vehicle initiates DPF regeneration cycles at extremely short intervals.

Measurement data & log data (retrieved via OBD / car scanner).
* Constant partial load (120-130 km/h): The engine runs smoothly. The boost pressure is stable at approximately 1.8 bar (absolute), the air mass is around 40 g/s, and the lambda value indicates a healthy excess of oxygen at Lambda 1.3/1.4.
* Acceleration / Load Change: When the accelerator pedal is pressed, the turbocharger quickly builds up pressure. The MAP sensor shows peak values of 2.4 to 2.5 bar (absolute), and the mass airflow sensor increases accordingly to over 80 g/s. Therefore, the turbocharger is delivering its full power.
* The core problem (Dynamic Lambda Gap): In the first 1-2 seconds of acceleration, the lambda value suddenly jumps to lambda 1. Precisely during these brief peak moments, the soot mass in the log increases sharply in steps. Only when the full boost pressure is reached does the lambda value increase again.
* Effect of the AGR valve: With the AGR valve connector disconnected, the car noticeably runs better, and the sudden increase in soot during load changes is significantly reduced.
Components that have been exchanged/verified so far.
* DPF: Replaced/Renewed.
* AGT Sensors: new.
* Lambda sensors: new (recalibrated).
* Mass Air Flow Sensor (MAF): Replaced.
* AGR valve: Replaced (adaptation values reset).
* Intercooler piping (pressure side): Hose between turbo and intercooler pipe replaced, pressure tested (1 bar) and demonstrably 100% leak-free.
* PCV (Positive Crankcase Ventilation): Removed from the intake manifold for testing purposes.
* MAP sensor: Clean, measures plausibly up to 2.5 bar absolute pressure.
* Intake manifold: Inlet/mixing chamber cleaned.
Current status & questions.

Given that the turbocharger, intercooler, and sensors are all providing optimal readings, it is likely that the problem lies in the fresh air flow or fuel mixture during the transition phase.

* Carbon buildup in the intake channels: Can carbon buildup deep within the intake manifold or directly at the cylinder head inlets cause the MAP sensor to measure full pressure at the inlet, while the actual air mass flows too slowly into the combustion chamber due to the restriction?
* AGR control / regulation delay: Have you had any experience with this engine regarding slow closing behavior of the AGR valve, or incorrect fuel injection adaptation values after an ECU reset?

"Has anyone ever experienced a similar phenomenon with a short-term lambda drop to 1.0 under load, despite full boost pressure? I can't read the injector values. When I cleaned the MAP sensor, I found about 2cm of grime on it, and the mixing chamber and throttle body were also very dirty."

Thank you for any advice!