That's actually the anti stutter valve ,its main and very important purpose is simple, IF your turbo seals blow and oil is literally poured from the turbo into intake system(as it does when seals go) your engine will rev its tits off till it goes bang this valve however allows you to turn ignition off and close the vacuum off which in turn shuts the valve and blocks the intake so you can prevent catastrophic engine failure or stop your car accelerating to mach 5 until it runs out of oil,most of us would dip the clutch to stop this happening but someone with no knowledge would simply press the brakes to try and stop the car this does not work you just burn the brakes out.It was invented sometime ago after the motor manufactures were sued in various countries due to the above scenario happening.Once the engine is running on its own oil you CANNOT stop it, without this valve in place, remove it at your peril.I. have a Laguna 2 which has gone through this event in at min and luckily the valve had not been removed,if it had and there had been an accident which is extremely likely someone would have been hurt and insurances DO NOT payout if the valve is missing, so beaware folks!
