I'm looking at the same turbo down under in Australia, but with stock
Fuel Pump
Injectors
Air Intake
BCS
I do have a HyperFlow TMIC and TurboSmart Kompact BOV
If you plan on upgrading injectors and pump later on it sounds like a good plan. If you don't forsee yourself doing that in the future the vf52 would be a better option/or whatever the japanese Legacy GT equivalent has in your hemisphere.(I'm guessing your 08 has the LGT style intercooler).
Reason being, the 18g tends to spool about 700-900 rpm later than a vf series so you lose a bit of quick off the line turbo time. Couple with that that running out of injector/fuel on the top end and cant run the turbo as far as possible and youve limited yourself to having a bit of midrange power and not as much elsewhere. Whereas the vf series will give you a broader range of power. you'll get a full low end power and nearly as much as possible on the turbo with minimal fueling issues on the top end.
The 18g will still be better than the TD04 turbo but not as strong as a vf series without the supporting fuel mods.
Due to fueling the 18g and vf52 will have relatively the exact same upper rpm possibility.
Just food for thought.
Edit:
Here's a completely non actual graph(not real in any way, i just used paint to make it) to show you the approximate difference between having the same fueling capabilities and where you'll gain with a vf model. In the top end I only seperated the lines to show see them differently but in reality they'll be pretty much on top of each other.
