ESPECIALLY if you are going/gone turbo..
In an internal wastegated setup, one usually cannot "swap" springs in the diaphram, as it is sealed.. You can only A. bleed it off prior to the wategate diaphram B.) restrict what it sees via a type of "boost controller"...
I do see alot of misinformation here, when it comes to turbocharging and it's fundementals..
if your turbo is from a Saab, then its a tiny turbo to begin with.. with a .42 AR compressor side, and a decent .48 AR turbine side.. They make PSI but not much CFM..
If you're dead set on it, get a manual boost controller.. they can be had for a few dollars on ebay.. At the same time, get a boost gauge and an Air/Fuel gauge.. You have to stay on top of that s**t, else she go boom, and you go boo hoo..