MAP sensors tells the ECU how most boost there is in the charge system... the ECU then uses the N75 to control the boost based on what the maps says it wants and the MAP sensor is seeing...
I have tried to interpret what you have posted to the best of my ability... If the MAP sensor shows a boost deviation above the requested boost in the MAP then the ECU will use the throttle body and N249/DV to cut boost pressure...
Over boost is subjective based on the info you have given... over boost can be caused by a number of things... If this is the problem you are getting then post some more specific info please, makes it easier to diagnose... as does making your posts readable
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