I currently have an ihi ball bearing vf34. It is pretty much the best small to mid sized ihi turbo available. Internally it is close to the same as 2871r but with a slightly larger compressor wheel and much better bearings. Bit it isnt cheap, usually around $1200-1400 new. I bought mine used from a friend who was using it on his s14 drift car, but the turbo made boost almost too fast for that car and wasnt the proper size for his displacement. His car running an external gate and was making 15psi by 3k with his built sohc 2.4l. The turbo is designed to be used with an engine around 2-2.2 liters and came stock on the jdm suby sti spec c which is considered to be one of the best versions of the sti made to date.
It should be able to make over 300whp easily with a higher compression engine. My other friend jake was running a vf30 on his s13 sr20 with stock cams, and a stock bottom end(8.5:1) and he made 295whp at around 18psi which was on a superflow dyno so as far as dynojet numbers go he would have been putting down close to 330 whp or so. The vf34 is the same internally as the vf30 besides the ball bearing center cartridge.
IHI VF34.
IHI VF34 Ball Bearing SUBARU Impreza Turbo Turbocharger : eBay Motors (item 280480450144 end time Apr-16-10 22:36:12 PDT)
I havent been able to beat on my car much due to a boost leak, but so far it pulls damn good for the little bit i have gotten on the gas. I should be getting the boost leak fixed by a friend this week and hopefully get on the dyno pretty soon.
Also it doesnt use a standard flange but you could easily weld an ihi flange on the bottom of a t2 flange and have good results. Both the cars i mentioned were set up this way with no issues.