Big fan of Vai and the Jem guitars, moderator on Jemsite, etc, what exactly are you trying to do? He uses Eventide harmonizers, but there are lot of breakdowns of his gear available. Have you looked on Vai.com?
W&T, Carvin, Elrick, and Fender Jazz basses
Bongo #54, Carvin #80, Fretless #295, Elrick #40