Where are you? As for how much boost for stock internals - that really hasn't been proven out to any degree yet. People blow up all sorts of stuff before they hit that limit right now. You should be good to run 10 psi, maybe 12 - maybe 330 whp. You could blow an engine at 6 psi with a bad tune/abuse so..... I think MM is running up to 14 psi but that's probably "you're on your own" territory for now.
Call Mazsport and if you can get in touch with Scott, he can tell you what WHP he's seeing from the kits at what levels of boost.
1+1=1 for small values of 1.