its the headlight leveling sensor, it attaches to the left rear control arm. it needs to be disconnected everytime you drop the left rear control arm to install a spring.
its not the headlight leveling system
its the intake manifold flapper motor.
http://www.ecstuning.com/Volkswagen-Golf_R--2.0T/Search/SiteSearch/Intake_Manifold/ES281203/