GT3071r its a ball bearing turbo (£900) which helps spool up quicker, I've had these doing well over 400hp, you need internals , 650 injectors (750 if your not bothered about lumpy tick over and cutting out at traffic lights!), and a decent clutch, pad clutch if you want to go to morrisons shopping in it or a stacker clutch if you just want it to go! Gearbox will be good if it has a good LSD or 4WD or it will go sideways instead of forward.
Garrett also have a new range of turbo's, GTX3071 which is good for 550hp and well suited to 2.0l, you could drop compression (with pistons) run higher boost and run 100hp nitrous for cooling. That would give you about 600-650
Above 500hp and you probably want to consider 750 injectors, changing the fuel pump and fuel lines cos they cant keep up with the demand which will make it run lean and then it will go POP!! At power in excess of 500 you may get better power using a stand alone ecu for fuel/timing or a piggy back one doing same as you will probably be outside parameters of std ecu.
Dont forget the little bits n bobs that all add up - bearings, gaskets, ARP bolt kits, fuel regulator, fmic etc etc
There are other mods too such as maf, you will want bigger inlet pipework for air flow which means calibration of the maf or you could just run an RS4 maf and the tuner should be able to install 'software' in the ecu to tell it its running the rs4 maf, this is easier than recalibrating the std maf which takes time and time is money!
Oh and a bloody good tuner that knows what he's doing, none of that internet map crap stuff
If you get the power bug, Its a money pit once you start!
