2018 Cooper S ALL 4 - Turbo UnderBoost - 120308 error code

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I have this Mini Countryman, has this issue of turbo underboost, this comes on at 2960 rpm,

I have tried all my best to find where the issue is at for this car but to no avail, I have had similar faults solve on other brand of cars, leaks to exhaust manifold crack, even intake bust but this Cooper is not giving me easy time at all,

I had the duct smoked from the turbo to the throttle, no leakage, with my past experience on some cars, exhaust wastegate can crack, so I used the chance to change the turbo, which uses electronic actuator to open the waste gate, yet still the fault persist. I need help please, I have attach some few data scan and freeze frame