I know what they do they releave the presure in the turbo manifold to make less boost. but what i want to know it how they work. does it need a vacume to open like the bov,or does it just work off the preasure of the turbo manifold. and if not what the hell do i screw into the top and the side of it. I'm thinking that they are for a boost controler (which i don't have) so do i just leave them open. thanks for the help