GFB 99-21 Subaru WRX STI WGA Wastegate Actuator (Tune Required)Massive Performance, Compact Size. Industry first diaphragm design the WGAs Silicone Nomex diaphragm uses a new bead retention design that achieves the largest effective area with the smallest possible outside diameter. This keeps the overall size of the WGA down whilst giving it more control authority over the wastegate flap, resulting in better boost control. Its like telling your turbo what to do instead of pleading with it! Longest stroke with