Subaru STi Spec C Anti Surge Fuel Pump Assembly Chassis & Suspension_Wheel Bearings & Seals and is as fitted to

and is as fitted to JDM models as standard

and highly accurate cam timing adjustments during engine setup or trackside tuning

Low temperature thermostats are most suited for vehicles driven "spiritdley" on either road or track where engine temperatures are likely to raise at a much faster rate than if the engine was being driven under normal road use

An increased thickness in the gasket is introduced around vital sealing areas and the design of this extra layer forms a much stronger barrier to prevent gasses / pressure / water and oil escaping from its designated area

Subaru STi Spec C Anti Surge Fuel Pump Assembly Chassis & Suspension_Wheel Bearings & Seals and is as fitted toThe Subaru Impreza fuel tank design is flawed particularly when running below half a tank of fuel. Its possible to encounter fuel surge on hard cornering and spirited driving as fuel moves around the fuel tank and away from the fuel pump. Fuel surge occurs when the fuel pump sucks in air as it is no longer submerged with fuel. This results in a fuel cut which from a driving perspective is quite aggressive as power from the engine is immediately cut.