There's no "stock boost level." It's a torque based system. Basically, the computer will command only as much boost as needed to hit 148ft/lbs of torque. So if it's cold out (denser air) and your engine is making plenty of power, it may only use 8-10psi to meet the torque target. If you're at high elevation or it's really hot out, it'll make 16-18psi of boost. However much it takes to make the torque target.