El power lo activas con tu pulgar con un boton que va en la misma palanca de cambios
En cuanto al boton "manual", esto encontré:
The manual button for starters ONLY works in 2 or 3 range, it does not work in D range. When engaged, it holds the car in second gear (2 range) or in 2nd and 3rd (3 range), and prevents the car from shifting down into first gear. It's basically for low traction situations, the car will start out in 2nd gear instead of first. Good explanation at www.surrealmirage.com/subaru/ click on "notes and tips" on the left, then in the drop down list choose "trans" and then click "manual button" at the top of the page. And visit http://bbs.legacycentral.org/ and http://www.ultimatesubaru.org/forum/
saludos y suerte