[heylinTTnz]

The factory one with a Bmc or K&N filter.

 

[heylinTTnz]

thanks. should i use the factory air box or buy a heathield so it is open?

Factory air box with a drop in filter, good enough for RS5 so should be fine for a 3.0 tdi, unless you are going for stage 2+ tuning and supporting mods for big HP, the factory intake is fine.