MKB 1 vs MKB 2: User Reviews & Comparison

I currently drive an A6 2.5 TDI with 150 hp, which has been tuned with a pbox to 180 hp, and I'm very happy with it. After the mass airflow sensor (MAF sensor) was replaced (thanks to the comments in this forum!).
I now have the opportunity to get an Allroad.
2.5 TDI, manufactured in November 2000, with 179 horsepower for sale. Now, my questions:
What is the 2.5 TDI 179 hp engine like in this model?
It seems like this engine is making a lot of noise.
(A friend of mine has a 2003 model, and it runs completely differently.) What changes were made?
Are there any known issues with the mass airflow sensor (MAF sensor) in this engine?
What about the maximum mileage, or the wear and tear on parts due to high mileage?
What are your recommendations?
'Thank you very much!'