Update!!!
Good news: turbo doesn't smoke anymore. After breaking in the new pistons for a couple of hundred of KMs (~500) I gave it a light push to see if the turbo works and what do you know it doesn't smoke anymore!... still keeping my fingers crossed though.
I don't know what cured it though... I just re-setup the engine bay and removed the catch can and stock BOV (or whatever that is).
Thank you all for your input!