A3 5V Turbo: Poor Performance Issues

Hello!
I am aware that this is not a diesel vehicle, but it would still be helpful if you could provide me with some information!
The problem vehicle is an A3, manufactured in 2000, with a turbocharged 5-valve engine producing 150 horsepower.
The problem becomes noticeable during normal acceleration, as there is clearly a lack of power! Instead of the expected 1.6 bar of boost pressure, my car only achieves 1.25 bar.
In addition, there's a slight hesitation or power loss, but it's barely noticeable.
'Work completed so far: LMM attempted, no success.'
Turbocharger replacement - unsuccessful.
Boost pressure solenoid valve - no success.
Exhaust system - visual inspection (catalytic converter): everything is in order!
Charging hoses, vacuum hoses - visual inspection, all OK!
According to the customer, the problem appeared overnight.
Have fun pondering! And thank you in advance for your help!
Best regards, L.G. Racer.

Hello,

How about the AGR valve?

Um, you probably mean 0.6 bar and 0.25 bar, right?

I would suspect misfires. Replace (or check) the four ignition coils and inspect the distributor.
* Check ignition timing, check lambda function, clean oxygen sensor.

*if none of this works: compression test

Hello,

Was the error memory read? Are there any other data available from test drives?

PS: What specific model of machine is being referred to here?

Hello friends!
Thanks again, it turns out it was the control unit.
I'm sorry I didn't get back to you sooner; things were a bit behind schedule.
Thank you very much.
Sincerely,
Racer!!