I was also confused before with the different variant of WRX
available and i decided to consult the Rex driver in another Subaru
forum and they clarified for me.
If i have understood correctly, below are the answers:
Basically there are 3 types of WRX from Subaru Japan
available:
1. WRX (265hp)
2. WRX STi (280hp)
3. WRX STi Spec C (280hp) - even higher end STi
For SG, we have the WRX(225hp) and WRX STi(265hp) from MI. However
the version here is a Euro export one. In other words, if you want
to ask what is our local WRX equivalant in the Japan market,
frankly speaking i do not know what it is since the model is not
available there. It has been created just for export selling
(that's why Praetorian111 always say he has a turtle Rex... not
tuned for performance 
).
Our WRX STi here is the equivalent to the basic WRX model in Japan.
All along, i thought the STi from MI is the real STi, now i know i
am wrong. The technical specifications are completely different
including the turbo booaster (a twin-scroll roll) and many other
more high techs in the Japan STi.
The final verdict from the Rex forum for those getting the WRX are
- if you are rich, get the Japan STi Spec C. If not, get the Japan
STi then. These 2 are only available from the PI here. If there is
still a money issue, then get the STi from MI which is only
considered as the basic WRX in Japan. If still cannot, then get the
WRX from MI. This also explains the different OMVs for the
different WRX from MI and PI especially the STi model.
Hope i have contributed correctly here for all...
