Thats not the way to do it, IMO.

Boost first, learn the tendencies of a turbo/sc kit...make as much power as you can reliable on the stock motor and enjoy it. If it goes, it goes. Then rebuild it and shoot for big power. If it lasts, enjoy hassle-free boost for as long as you can. Thats my philosophy. Why fix it if it aint broke?

Have you had them adjusted correctly? Are you doing the valve job yourself? Is the idle steady?