I was having a look at the rd28 supp and noticed this tank that I thought might be emission related but turns out to be a vacuum canister. It is not there in my car and some one has fitted an air horn pump. Now I have removed the pump but want to know if it is a vital thing to have. I have heard that it is for brakes and clutch but I am not sure as the car won't be here until next week and want to get a RWC done so want to cover as many things as I can. Pic for attention. Is it ok not to have this installed?

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