At what point you get full boost depends on a lot of things, the size of the turbo being the largest factors.
Install the -31, connect up the control pipe to the -31 adjust the preload to achieve the desired boost and away you go...

i would start off with about 1mm preload, and see what boost you get.

I think the max preload you are supposed to run on a -31 is 3mm if memory serves me well

I get full boost about 3400 rpm under hard load
Cheers

Steve