At the moment, I am unable to take on a full project as I already have a couple going. My advice however is that if you are truly interested in a decent turbo setup that you put aside £3-3.5K for a basic T2 conversion, and get back to me soon.
Please note that a GT25R turbo for example is a beast, and as such standard engine internals would not take that kind of power relaibly, so forged pistons/conrods would need to be invested in, if done right you would be looking at easily in excess of 200bhp from this, as opposed to around 130 ish from a standard T2, but to really make the system work to its ultimate potential would require quite some changes to the car such as the following:
GT25R setup
*Full 2 inch turbo back exhaust + cat (if you ever want to pass another MOT) ~£4-700+
*Forged engine internals + rebuilt bottom end. ~£2K
*Turbo ~£700
*Manifold ~£350
*Intake pipework + Intercooler ~£500 (consider charge cooler)
*e-Manage ECU + remap ~£500
*Uprated brakes to GTIR spec ~£300
*Nismo paddle clutch
*Removal + refitting + rebuild labour inc parts ~£1200-1500
Rough est bhp ~220
You might want to sit down before you add that lot up..
Yes it sounds madness, but there are no compromises in that example it would be one of the most powerfull K11s in existance.
The point being there however is YES you could do it for much much less, but you would loose out in one way or another.
For example stick with standard engine, and put a thick head gasket on it (nasty) and save about £1700.. I would not guarantee it to anything more than 6psi however. Yes people have done more, alot more, but then many have gone bang. Its simply a matter of time. If you cut down a simple spec system, with limited potential you get the following:
T2 setup
*Stock exhaust with modified down pipe. ~£150
*Thick headgasket ~£200
*Turbo ~£200 (about the price you can get a decent one for second hand if your lucky)
*Manifold ~£350
*Intake pipework + Intercooler ~£500 (consider charge cooler) this doesnt change much - its worth doing right regardless.
*e-Manage ECU + remap ~£500
*Uprated brakes to GTIR spec ~£300
*Nismo paddle clutch ~£300
*Removal + refitting + rebuild labour inc parts ~£800-1200
Rough est bhp ~120 ish (dont forget though a MASSIVE increse on torque, so midrange it would wipeout any NA K11.)
About half the price, for about half the power..
Anyway that gives you an idea of what to expect to pay.. etc