Any form of bleed off boost control no matter what it is, will only ever work by bleeding air off the control line. If the waste gate actuator doesn't see the pressure it requires to open, then it will stay shut. It's that simple in most cases.

If you or your tuner want to use a stronger spring then feel free to ask for one, but I personally would be using a -31 to achieve your target boost pressure. There is no real need for anything stronger.

Going back to your power graph thread, the other graph that was posted matts 3dr was live mapped by us on a -31 at over 36 psi on a T34.48, and makes massive boost by 3krpm. It doesn't need a stronger spring.

If your boost control system does not.operate correctly then I would personally be looking to change that rather than an actuator that we know works perfectly at these operating pressures.