I used
https://www.auto-rx.com/ on my old VW Passat.
The VW 1.8 turbo engine was renown for this problem. Poor oil change routine (not by me) and high turbo temperatures caused the issues.
I followed the cleaning program to the letter.
I could not believe the amount of filth that was removed at filter changes.
The results were amazing for me. I could see how clean the top of the engine was through the oil filler cap.
I also kept up with the maintenance program afterwards, with no more issues.
As I said it worked for me!