GR-Suspension, Handling, Stiffening
If all you want is to upgrade the gear, here is what is needed for 2008-2014 vehicles.
Actual parts needed:
34110VA120: Perry Subaru Subaru Gear Assembly 34110VA120 | The Subaru Source These guys have a promo code WE-STI that is still good 6/27/2018
OPTIONAL PARTS(links below as well):