A turbo manifold won't bolt up to the 2GNT engine -or- a Garrett turbo, so that's out. You'll need a custom manifold, probably best to go with one from Star or Hahn since making manifolds is complicated and costly (and they have a tendency to crack when you hang a heavy turbo off them).

Making a custom FMIC setup and downpipe actually turns out to be more $$$ than you might think as well.

You'll also need to figure out the oil lines (and possibly water lines) to cool the turbo.

All in all, it's probably not much more to go with a kit, or at least to buy *some* of the parts from the kit.