1.2 TDI CFWA P0087 Delphie CR Injector

Hello fellow DIY enthusiasts,

I've been having problems with my Polo 1.2 TDI for a while. After the HDP (High-Pressure Diesel Pump) failed, I replaced everything and cleaned it all.

Now, 50,000 km later, the error code P0087 appears: fuel system rail/system pressure too low.

Das Fahrzeug fährt normal, einzige Auffälligkeit ist, dass er sehr laut nagelt wenn er kalt ist. (Nur beim ersten Anfahren. (Das Nageln verschwindet nach kurzer Zeit). Zusätzlich sind Leistungseinbußen bemerkbar (Anfahrschwäche und auf der Autobahn im 5. Gang certainly.
Sometimes, he just can't seem to break out of it.

I know it's a 1.2, but there's still more potential.

Can someone tell me if there's a faulty injector here, or what else I should check?
Thank you in advance to everyone who is helping!

I checked the tank for wood shavings, and there are hardly any. A small amount of shavings is normal.

Best regards,

Marco.