2.0 TDI BKD: AGR Valve Problem?

Today I discovered that the area behind my EGR valve is very oily and dirty, so I removed the EGR valve and the throttle body. I'm not sure where this contamination is coming from. It's located behind the EGR valve, on the cylinder head, engine block, and intake manifold. The intake manifold itself doesn't seem to be the cause.

"I was shocked to see what the EGR valve looked like after only 20,000 km. There was a 3mm thick layer of soot all around, which is definitely not normal! I cleaned it thoroughly before installing it. I strongly suspect that the dirt is escaping from the EGR valve outwards through the hole visible in the photo. Is that possible, or is it unthinkable? What is the purpose of this hole under the pressure sensor? The driving behavior is normal."

How can the engine control unit be modified so that blocking the EGR pipe with a plate does not trigger an error, or to what extent can the feedback rate be reduced using VCDS?

Thank you for your help!

The hole is the reference air vent. If anything comes out of it, the part is defective. This happens very often.

You can't adjust the AGR rate using VCDS on a BKD engine. Ask Rainer; he can help with that.