Turbo Failure: Removal & Repair Guides

I drive an Audi A6 2.5 TDI, manufactured in 1999, with 105,000 km on the odometer, and I believe my turbocharger is faulty.
LLM is perfectly fine. A grinding noise occurs at speeds between 1900-2500 RPM, but only during rapid acceleration.
As soon as the noise disappears with further acceleration, the engine experiences a noticeable increase in power. The mechanism for adjusting the impeller blades is also working (and has been checked by a mechanic). Furthermore, the engine delivers its full power and can reach up to 4000 RPM on a straight highway.
What could be causing the poor performance at low speeds, the metallic grinding noise, and the uneven power delivery that is different from how it used to be?
I suspect it's the turbo.
Can anyone give me advice on how to remove the turbocharger myself, or where I can find informative technical literature or resources online?

Thank you in advance for all your answers!

Best regards,
lars75

Hello Lars,

Was the error memory read? Did the workshop perform a test drive (target values in "Troubleshooting and Instructions")?