Audi a6 110 tdi, what engine code

[jay_tqs]

Hi, I am the owner of a 110 1999 c5 a6 1.9 tdi, I am wondering what the engine code should be and where I can find it, new to the a6 so just looking for some info, so I can make progress with a few little mods,
any info on this engine is greatly appreciated like, the weak spots ( turbo vanes, etc?) that can be rectified with a bit of work and cleaning?

 

[adamss24]

Should be either a AFN or AVG...