I've played around with valve lash quite extensively, I do not think there is any advantage to changing stock valve lash specifications in a forced induction application. I use idle vacuum as a guide, personally I first adjusted the lash at about 15K because the ticking at idle was annoying, I went a little tighter than stock and idle quality suffered tremendously, I then adjusted the lash again back to stock spec and the slight ticking (typical) returned, but it idled perfectly (maximum vacuum).