Audi SQ7 4.0 TDI CZAC – Low boost at low RPM

Hi everyone,
I would appreciate some opinions from people who have experience with the Audi SQ7 4.0 TDI (engine code CZAC).
Vehicle:

• Audi SQ7 4.0 TDI V8
  
• 2017
  
• Engine code CZAC
  
• Mileage: 232,000 km
  

Complaint:
The vehicle has noticeably low boost / weak response in the lower RPM range. Above approximately 3500–4000 rpm it pulls much better and actual boost gets much closer to specified boost.
Intermittent DTC:
P0299 - Boost Pressure Regulation
Control Range Not Reached
Freeze frame:

• Engine speed: 2424 rpm
  
• Engine load: 100 %
  
• Vehicle speed: 141 km/h
  
• Coolant temp: 90 °C
  
• Intake air temp: 36 °C
  
• Ambient pressure: 970 mbar
  
• Specified boost: 3250 hPa
  
• Actual boost: 2740 hPa
  
• Difference: -510 mbar
  
• Charge pressure actuator specified: 95.0 %
  
• Charge pressure actuator actual: 94.4 %
  
• Air mass actual: 1398 mg/stroke
  

The fault is intermittent and does not appear on every test drive.
What I have checked so far:
DPF differential pressure:

• Idle: 6 mbar
  
• 2500 rpm no load: 43 mbar
  

These values seem normal to me.
However, during WOT logs I can see DPF differential pressure peaks of approximately 800–1000 mbar, which seems very high.
Boost logs:
At low RPM there is a significant deviation between specified and actual boost.
Examples:

• 2003 rpm: specified 2858 mbar, actual 2002 mbar (-856 mbar)
  
• 2812 rpm: specified 3173 mbar, actual 2343 mbar (-830 mbar)
  

At higher RPM the deviation becomes much smaller:

• 4008 rpm: specified 3400 mbar, actual 3310 mbar (-90 mbar)
  

Electric compressor (EPC):
I also logged the electric compressor.
The EPC is definitely being commanded:

• Requested speed up to 72,000 rpm
  
• Actual speed up to 66,000 rpm
  
• Current draw up to 120 A
  
• 48V system voltage appears normal
  

The EPC reaches approximately 59,000–66,000 rpm when 72,000 rpm is requested. I am not sure whether this is considered normal on a healthy system.
Questions:

1. Do you think DPF differential pressure peaks of 800–1000 mbar under full load are realistic for this engine, considering that idle and no-load values are normal?
   
2. Is it normal for EPC actual speed to remain around 59,000–66,000 rpm when the requested speed is 72,000 rpm?
   
3. Would you focus more on the EPC / EPC bypass flap, turbocharger switching system (AVS / sequential turbo operation), or on a possible exhaust restriction?
   
4. Has anyone seen a similar P0299 issue on a CZAC engine where the root cause was not a boost leak?
   

I have attached the latest boost log.
Any thoughts or experience with this engine would be greatly appreciated.
Thanks!