Multivan 96KW (AXD) - VW Van for Sale

Hello everyone,
I've noticed a change in the engine's performance in my 5-cylinder TDI over the past few days, or at least I think I have.
The engine has now run for 1000 km. When accelerating or when the engine is working on an incline, especially between 2000-2500 RPM, it feels like one cylinder isn't working properly. There's a slight vibration, and there's a kind of periodic gap in the engine noise, similar to how a four-cylinder engine might sound if it's 'running on three cylinders,' but not as pronounced.
It might be typical for a 5-cylinder engine, but I think it's only started happening recently.
What could be the reason for that?

Hello,

It's best to read out measurement block 13, specifically the idle speed control, and also search for information on this topic.

Best regards, Rainer.