Hallman PRO-RX-BK Boost Controller, Black

My wastegate is set at 8psi, i want 12psi. Will this add only 4psi? Whats its minimum setting? Thank you

Dose it include another spring that is heavy duty with the kit?

Does this come with a mounting clamp?

Wondering what others are seeing for boost increases per turn? I'm 2 turns in and netting a .8-1.2 psi increase. Around .5 increase per turn.