I have just bought a 2004 WRX STI that was imported from Malta back in 04. I'm just wondering what turbo it is likely to have fitted? IHI?

 

yes

 

Cheers.

Presume the VF34 or VF36 Roller bearing turbo then!?

 

Probably a VF34

 

Ok, cheers.

Are there any upgrades to turbo that can be done without needing other bits changing (e.g. up/down pipe, headers, manifold, etc.)? I'm currently running 348bhp & 356ft/lb and don't plan any changes in the immediate future, but did wonder if I could upgrade turbo any further without major mods to other bits. For reference should I locate a suitable turbo.