Disclaimer: This is my experience, as you can see even from nuffy's post above.. setups and results are wide and varied
The reason Suzitech would be aiming for that 10psi mark is cost, once you go above this mark the complexity increases:
- Vitara rebuild will handle it easily
- Chipped ECU will handle the fueling up to 10psi quite comfortably
- AFM can manage it (as standard ECU will be using this)
- Clutch doesn't have to be too insane to put the power down
- Standard GTi box _should_ handle it if looked after (the HD won't help)
- Standard pump/rail/injectors can provide enough fuel (perhaps even without aftermarket reg when using the chip, but reg would probably be a good idea)
I would probably say that on 10-12psi on a t25/t28 at around 100-120kw you are going to be pretty happy. Even if you build a setup with turbo that is capable of making bigger numbers, and just run it at lower boost with chip etc. and just work your way up it will be a good way to go (but spend as much on internals as you can afford

).
I have always seen 150kw - 160kw as 'the' mark. With my third turbo setup that is currently being built I am trying to edge closer to it. I am only mentioning this to show what I have been through.. and I know there is far more I _can_ do.and 150/160 is a decent stretch.. in reality I think I will be coming in at about 130-135. (Obviously the kw atw figures aren't absolute.. but they give a ballpark at least)
I can tell you, squeezing an extra 5kw from ~120kw is a serious exercise and everything starts getting a lot more involved. From the setup I am taking off the car I ran 12psi and managed ~110-120kw... to go further I had to swap to:
Intank Walbro fuel pump + bigger fuel filter (some do surge at the same time)
Custom fuel rail and rising rate reg (and all fuel lines/fittings in engine bay)
Larger injectors
Bigger turbo (up from t25) which also includes new manifold, dump, exhaust etc.
O-Ring the block
Ported head
Full aftermarket computer and swap AFM to MAP (tuning of chip will struggle above 12psi even with larger fuel system, and AFM is well and truely maxed out)
Clutch to get the power to the ground
Also add to that an LSD to stop the single stripes, and potentially a Cultus box if you can find one (I haven't puree'd my current box but won't be long).
Probably plenty more I haven't even come across yet, things like Electronic Boost Controller to try and control the boost with a bit more granularity and perhaps ignition (bigger single coil) or coil packs.
Like has already been mentioned.. if you want a 160kw setup and street proven performance.. I think your option is fairly clear. The cars in QLD are making these kinds of figures regularly. Also talk to the Swift guys turning up to the drags... they are all getting into pretty serious setups and they are all great guys who are willing to share information.
Checkout the Dyno/QMT page and have a chat to the guys making those kinds of numbers, sure they would be happy to help.
My estimates from my experience and raw cost of materials and specialist labour would probably put the price in at the 10-12k ballpark... so you have to like your Swift a fair bit
If there is one tip I can pass on is, if you are serious, buy a full aftermarket computer as soon as you start heading towards 6-10psi/100kw with a chip. Not only will you get the most out of your mods, but it will save you headaches of trying to get the standard ECU and sensors to do things they just weren't made to do.