Download directors cut,

open Program files,resources,Mafia2Data.dmg. make your own dmg with the same name,

copy data to that disk. Delete Mafia2Data.dmg in the mafia 2 app. Now you can edit the Mafia2Data.dmg that you made yourself. You can add dlc’s or replace any data. 

needed:

-disc utility

-mafia2 directors cut