First set the actuator preload to get your initial starting point, this video explains how this should be done:
[video=youtube;p12g1PpIcjE]http://www.youtube.com/watch?v=p12g1PpIcjE[/video]
Once you've set the preload you'll need to drive the car and see where you're at in terms of peak boost pressure, this will require a run in 4th gear. Next shorten the actuator arm and road test the car again, if the turbo is over boosting then the arm length will need to be increased or if it's still not reaching the desired boost pressure you'll need to shorten the arm some more. A couple of tips when doing this are to adjust the arm 1 turn at a time between each run down the road (it's a bit tedious but once you've set the actuator arm length you shouldn't need to touch it again), and also leave the C clip off of the actuator connecting pin until you have finalised your adjustments (repeatedly dropping the clip and burning your hands numerous times on the very hot turbine housing whilst trying to remove and reinstall the clip will become very boring very quickly), don't worry about the actuator arm disconnecting from the wastegate whilst driving as all that will happen is you'll lose boost pressure, no damage will be caused. Once your finished just remember to gently nip up the lock nut on the actuator arm.
