what does this valve do

CAN ANYONE TELL ME WHAT THIS VALVE DOES AND WHY IT HAS BEEN DISCONNECTED,THE PIPES THAT ARE SUPPOSED TO GO TO IT HAVE BEEN BLANKED OFF,I DONT WANT TO CONNECT IT BACK UP BECAUSE I DONT KNOW WHICH PIPES GO WHERE OR IF IT WORKS,iIT IS POSISITIONED ON THE O/S FRONT SHOCKER MOUNT ,WHEN I START THE ENGINE IT IDLES AT 2000RPM AND AS IT WARMS UP IT DROPS TO 1000 AS IT SHOULD ALL HELP WILL BE MUCH APPRIECIATED
CHEERS   89 golf gti cabby
DAN COOKE

Never seen one have a free Bump

any one else  :dontknow:

Later cabrios had this and an extra diapharm thingy near the meter head that tintop DX engined cars don't have. No idea what each device does but somthing to to do with starting and cold idling control :dontknow:

its idle control stops the car dying when at a junction if you disconnect while running the car from cold the revs will drop iirc