That actually not a AAZ pump. It has no turbo boost mechanism. Looks to me like that's a 1Y pump. the non turbo version of the AAZ.
That thing is a automatic Coldstart regulator. its a switch that extends (i.e lowers the idle) after about 10 mins when the engine is warm. Instead of having a cable operated coldstart "Choke" like the older diesels this one automatic.
I cant find part numbers but in the German manual its labeled as
Stellelement für Leelaufdrehzahlanhebung N123
roughly translated:
Idle control setting element N123
other than a slight rough idle at starting this is not really essential to operation.