tons of turbo's fit the WRX, but you have to have the right setup. You shouldn't replace your turbo before you are at least stage 2.5 with upgraded fuel pump, fuel injectors, etc. I believe they come stock with the vf22 or a TD04 or something like that. The STI has the vf30 or vf34 i think. I was looking at putting a vf34 in my wrx once I get there. You can get stock WRX turbo's for really cheap though from people that have replaced their old ones if you ever blow your turbo. I'm lookin for one with a faster spool up, more power through lower rpm's, etc.