I was doing great at 5-6 psi, maybe 7 psi with my legacy turbo and 8-9 psi it felt strained and didn't gain much power going over 7-8 psi. Shiv says it maxes out at 230hp but we have some guys making 240-250hp on the dyno with them (est crank).
I really love my VF22, as it gives me fast boost at decent RPMs, and gobs of top end vs the legacy turbo. I let several people who autocross try it on fun runs and all claimed they felt there was no lag. In actuality there is minimal lag, but the legacy turbo feels like a supercharger