Here is Seb@SpecialtyZ's 370Z at up to 12 PSI. Look at the torque band...
The Specialty-Z GTM Stage 2 Build
I've honestly not seen anyone with anything higher than Stage 3, unless you are talking about Bullitt's car which is aiming for 1000 whp. There's the G37 making over 600 whp with over 12 PSI.