I measured the actuator on my stock '05 Audi 1.8t K03 with following results.
Listed is the PSi applied to actuator port and the corresponding rod movement:
3.5psi .25mm;
4.0psi 1.2mm;
4.5psi 2.8mm;
5.0psi 4.6mm;
5.5psi 6.2mm;
6.0psi 7.7mm;
6.5psi 9.2mm;
7.0psi 10.7mm
I did not measure above 7psi as there are only 10.4mm worth of threads on the actuator rod to move the locking nut over. Three full turns of preload seals the waste-gate flapper nicely. Any more is not (normally) necessary because the N75 determines actual boost by bleeding pressure from the actuator.
A person might think that tightening down the nut each full turn gains 1/3 psi in boost but again, the N75 controls boost by bleeding off pressure from the actuator and thereby keeping the waste-gate closed.
Keeping the waste-gate snugly closed is only effective in fighting exhaust back pressure in the turbo until the ECU decides the boost level is sufficient and drives the N75 to allow the waste-gate to open. So in summary: If your actuator is not pre-loading your waste-gate enough then cranking down on your actuator adjustment will help (assuming your waste-gate is in decent shape). The duty cycle of your n75 valve is the final answer to all these questions. You do not want it down near 0%. That would mean:
your waste-gate is going bad or,
your actuator is going bad or,
the actuator adjustment is too loose or,
your pressure hoses from the compressor housing, thru the N75 to the actuator are bad.
I am guessing anything above 15% duty cycle would be fine, otherwise crank down on the actuator adjustment and see if that helps raise the duty cycle. If it does not then you have to start looking at the other previously mentioned items.
Just understand that you can't hurt anything by cranking down on the actuator rod adjustment. If you do crank it all the way tight and improve your boost to about 7psi then your N75 and/or its pressure hoses are dead.
