You'd definatly need the AFM, but you don't necessarily need the airbox, you could always position the AFM and use a pod filter instead of the box and use some flexipipe to join the AFM to the turbo. This is just another option.
You'd probably have to go flexipipe between the AFM and turbo because to get the 3 sections of pipe required to join these 2 in a factory setup would be rather difficult and expensive, just one section costed me $140 trade or $168 normal and they had to order it from Japan (3 week wait) god know about the other 2 because one of the sections is metal.
-EDIT-
Ohh shit sorry I just realized what I said, you may not need an AFM, it depends on your computer. If you use a stock GT4 factory ECU then you will, but if your going to buy an aftermarket and have it tuned it would probably run a MAP sensor rather than an AFM anyway, which would be better.