Thanks for asking, for a suck through system nothing...
But I guess you are using the MG Metro setup which is blow through...the inlet manifold and float chamber (top) need connecting.
This is done by a pipe from the bolt flange of the carb that goes from there to the float chamber vent.....that will be the one you have seen, its the black pipe on the photo.
This carb needs a spacer block with a pipe take-off between the carb and manifold, and a pipe to connect the 2, which would do the job as per standard turbo setup
If you bought it I would do that for free.
I do have a spare turbo carb plenum too.
If you need any diagrams on piping them up just ask, as with the ECU, fuel pressure regulator, wastegate and a bleed off valve it can get complicated, but compared to a bi-turbo range rover its ABC, and more reliable...hahah