Have we got a diagram?
I had a vacume noise in my car and after having a nosey under my dash found a vacume line sucking in air and was running out through the bulk head, i tugge dit gentaly and it came off whenever it was attached to on the inlet and I have had a good feel about and can find the ocation it was attached to, or if it should be open (i think not) , car still runs and drives ok but I dont want to risk leaning out and going bang.