I would have thought the 6152 would have had to be 27-28+psi to do what it did last night. Who would have ever thought that the 6152 would have such power at 20-21 psi on the right setup and probably never find its true capabilities.
I'd think the credit is due more to the heads than the turbo. In all fairness, I'd bet his ported TA heads flow a TON more air than your average iron head (not top flow number, but throughout the range). A motor with your average ported irons would probably need 27-28psi to go that fast?