-injectors (new or mod the stockers)
-larger TMIC or FMIC (the latter is prob overkill, from what I've read)
I'm assuming you're not just talking about a stock WRX w/ stock exhaust, stock up-pipe, stock ECU, etc. Correct? One would assume you've taken care of those mods before thinking about slapping a VF22 (or any other turbo) on.