I agree the stock wastegate isn't sized for the increased flow in the upper range. However, the "spike" you illustated earlier in this thread was not at high enough flow to overwhelm the wastegate. It is a control dynamics problem. We are really messing around with the pressure differential that drives the turbines.
By logging boost with the wastegate completely open, I believe it would not be too hard to calculate the new size for the wastegate orifice, such that it could be once again in the DDE control loop... hmm, someone already thought of that
I applaud your efforts. EWG is best practice for customized systems. Today control of an EWG is done with PWM in a negative feedback control loop - just how the DDE does it. You have your hands full if you are using springs and manual bleeds. Not impossible, but very difficult if you want that boost curve to slope down at high load, to control rotational speeds. Best of luck.
