VF36, VF37 & VF38 are the TS.
Judging by previous threads started, he has an MY01 WRX.
Any of the single scroll VF turbos will be a good upgrade for an MY01, some obviously better than others. My suggestion is get the newest one you can afford. While its getting done, I'd suggest deleting the cat converter in the up-pipe. As the car is 10+ years old, a drop in Walbro replacement fuel pump is definitely a good idea.
These will be fine with any of the various
ecu flashes (Verso, EcuTek, OpenEcu, evoRso etc)