This may help, Mike Rainbird just posted it up in GD:
First set the wastegate preload to 9 psi by temporarily connecting the compressor outlet to the actuator using a short piece of tube.
This should be about half a hole of preload if using a -31 (as in when you place the actuator rod over the wastegate shaft, you can see half a hole showing).
Then reconnect all the amal valve piping back to normal.
The restrictor in the amal union that normally goes to the airbox needs enlarging slightly. Change this to around around a 1.5mm increase using a suitable sized drill bit (it might be worth going up in 0.5mm steps, as you can always make it bigger, but you can't make it smaller!).
With this done the boost should be holding about 15-20psi.
If want more than the above results you will need to enlarge the restrictor in the other amal union, but like the above, go up in 0.5mm increments for the same reason.
Once you get NEAR what you want, THEN use the actuator to fine tine the boost limit. But DON'T slacken it to reduce boost (in case the restrictor was opened out too much) otherwise the wastegate will rattle. Also don't wind it in more than a holes worth - open the restrictor a bit more instead to get the required bleed off.
Hope this helps?