I rebuilt the engine already with H-Beam rods. The alternative to buying a gtx was to repair my old K03. Seems a waste if you'll pardon the pun.. I understand that there are envelopes not to push past and that's all I'm trying to do is reduce the chance of that happening by asking questions.
the short answer is the wastegate is controlled by the ECU.
it should have a proper operating range such that
1) it is tight enough to hold the maximum desired boost when there is no pressure in the wg control line (N75 WGDC is >95%)
2) the minimum pressure required to open the wastegate is low enough to allow good part throttle behavior (N75 WGDC is <10%)
3) the operating range of useful wg control line pressure results in as linear a response as possible
To elaborate on 2, the ECU controls load via two main methods (torque intervention via ignition angle notwithstanding): 1) throttle plate angle and 2) wgdc.
Below cracking pressure (aka base boost), load can only be controlled via throttle plate angle
Above cracking pressure, load can also be controlled via wgdc
This is all applicable to all kinds of forced induction applications, it is not unique to Audi or even Motronic.
It is a bare requirement to understand all of it before even beginning the tuning process.
