TDI No Power After Start - Troubleshooting

hello everyone,
This is a cry for help!
I've been struggling with a problem for two years now, and no one has been able to help me so far.
After starting, my TDI (1Z, 90 hp) has no power (it feels like it's in limp mode, but the error light doesn't come on). It only starts running normally after I rev it once to around 3200 rpm (whether it's at idle or under load). Then, as soon as I turn it off and restart it, the problem starts again.
'The only error message is: 'implausible signal from mass airflow sensor (intermittent)'. The mass airflow sensor has already been replaced, as has the EGR valve. The voltage at the mass airflow sensor is fine, and the resistance at the EGR valve is also within the acceptable range. The engine control unit has been temporarily replaced, but that didn't solve the problem either.'
Can someone help me?
Thank you very much for your support.
Best regards from Smøre.