If i were you i would start with checking to see if the green line is clogged. and make sure that the wastegate bypass solenoid (the small thing the red and green lines run to) is working and not stuck shut. Somewhere in this system is your issue because when you bypass it by disconnecting the red line the wastegate actuator has no issue keeping the wastegate closed(you have no issue building boost).Running JP on stage 1s and stock turbo.
With the redline disconnected, I can spin the tires on a pedal mash resulting in lots of black smoke and a SES light. The code is the standard wastegate controller malfunction. My gauge comes very close to 30 PSI
When i connect the red line, life is much slower. Mashing the pedal does not cause boost to raise as quick and there is no spinning of tires to be found. PSI maxes at just over 20 with sustained WOT.
Does this indicate a need for wastegate adjustment? Any thoughts on how many rotations are needed?
The wastegate bypass opens under acceleration and allows boost to bypass the wastegate actuator thus keeping the wastegate closed building boost up to around 16.5 psi stock then it starts to close keeping the boost from bypassing the actuator which then opens the wastegate thus limiting the max boost level and overspeed of the turbo.
You will need a boost fooler to keep the ses light from coming on above 24psi and this will also keep it from defueling above that.