LMM Curve: Troubleshooting Turbocharger Issues on VW T4 AHY

Hi everyone.

I have a question: I had a dynamometer test performed on my T4 AHY engine with the mass airflow sensor (MAF). See the image below.

Why are the target and actual values different when idling, even though the mass airflow sensor (MAF) is brand new?

I'm having a problem where my T4 is going into limp mode.
Error 17964: Turbocharger boost pressure regulation - Lower limit exceeded.

All hoses have been inspected; VTG certification is also available.

Before replacing the mass airflow sensor (MAF), the boost pressure curve looked like this (middle image).

After the exchange, see the image above.

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