If you dont already have one, get a catless up-pipe while your at it. the standard my02 up-pipe has a catalytic convertor in it which will more than likely break apart eventually and sending pieces of the cat through your turbine blades. Not good.

Its only two extra bolts to remove the OEM my02 up-pipe and its easy to do while your there.

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RS Liberty - Because WRX's are only good for parts...