They chose a 51mm inducer/53mm exducer for their Stage 1 application for enthusiasts who are looking for up to a 40% increase in power while maintaining stock spool characteristics.
It is recommended to use 850cc or 1000cc injectors for 91/93 octane and 1000cc for E85 applications. They utilize a Turbosmart wastegate actuator to help stabilize boost on this high boost application.
They do not recommend large diameter aftermarket exhaust manifolds/headers as a diameter over 1.25" drastically reduces exhaust energy and will move the power band to a normally less than desirable range for a street driven car.
Stage 2 is recommended for use if using E85 at elevations above 3500ft.
Aftermarket oil lines may require a restrictor.
WRX and Forester models require OEM STI oil drain outlet and OEM STI coolant hard lines.