I need to firgure in what my vacuum will be to get the tial BOV my engine idles around -10vac to -15vac but if you rev up a little it will drop too -18vac to -20vac. So when ordering the spring which would be the right vacuum. They say to be a t idle but if you let off the gas the vac will fall to -20vac because of the rpms being up falling down. Thanks for info.