Basically all you have to do is change from a 6 psi pulley to a 9 psi pulley, which probably also require a different belt i'd assume. Do you currently have a bypass valve? I don't think you HAVE to have a bypass for 6 lbs, but you do need one for 9 lbs.
The standard bosch bypass valve that Vorech and all the other companies sell with there basic kits is enough for anything under 10psi. If your upgrading to a 9psi pulley, you wont be seeing 9psi as often as you think, unless you drive around at WOT all the time.