Finn is correct, the 2.0 wrx ( yours) has a catted up pipe, the classic catless up pipe is the same dimensions as the sti catless up pipe so it will fit but the classic will have no place for your cat over temp sensor that is located in the the up pipe on a newage car, this can be overcome. By removing it and fitting a resistor in it's place.
As for turbo don't expect anymore than 280hp from your standard td04, a move to a vf turbo is a wise move as the turbo will be almost off when changing the up pipe anyway, a vf will take you over 300hp but you will then be limited by your standard injectors.
Fit a set of sti pinks and you should see over 340hp providing you have the rest of the supporting mods (full decat, free flow filter, sti intercooler or at least a sti or samco y-pipe).
A 3 port boost control solenoid is also a good idea.
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