Help to repair my car. Fiat Brava 1.9 JTD

Hello friends, I have a problem with my Fiat Brava 1.9 JTD, they made it full engine 3 months ago and it seems that it failed again. I am going to send photos, video, consult to see who with experience can help me repair it since the previous arrangement came out very expensive and I want to see on my own if I can learn more about the topic to keep my car my car.

To start I tell you that the car was fine and the injectors began to fail. For this reason I bought cleaning and the same day that it takes it even if it is a coincidence or not the engine began to throw white smoke and taca taca and fails a lot.

I saw that a lot of oil came out of the engine and looking for the leak it seems that it is a hose that was missing from the engine that goes to a black box.
I would like to know what the black box is and if it is nomal that works with oil.
ATTACHED
PHOTO

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THE BOX