Lifting off the throttle in a turbo motor creates a pressure spike in the intake tract. This shock can decelerate and potentially damage the turbine/compressor wheel and bearing. Anti-surge valves mounted between the intercooler and throttle body help relieve this pressure. Taking things one step further, instead of relying on vacuum pressure, Ford actuates the valves electronically. Consequently, Ford is able to open and close the anti-surge valves not only to relieve pressure spikes, but also to smooth out boost delivery and reduce the whistling noises often associated with turbos.