Exhaust valve code on ECU

My k13 micra 1.2 dig s has had the same ECU fault 're appear on several occasions.
The car has been into a main dealer and at first they said they found a loose connection on the sensor for the exhaust valve. This was then made good but fault code came back and every time it does the car goes into limp mode until stopped and restarted then the limp mode clears but the warning indicator light stays on.
Nissan main dealer has now quoted me £945 for a new throttle chamber assembly.
Has anyone had a similar issue.
The car does sometimes feel a little juddery when the throttle is used.