I hit 15 psi @ ~2500 rpms. 20-22 psi by ~3000 rpms. (4th or 5th gear pulls).
I fixed my manifold leak and now can actually build so much boost downlow that I get a knock flash... my tune previously was based around slower spool because of my exhaust leak.
Even with a pretty bad leak, I spooled up on par with a VF30, if not a little better.
Boost begins building @ around 1000 rpms... very little (ie- 1-2 psi), but it starts.
I am running the twinscroll VF36 off the Version 8 Spec C.