boost pressure issue
 

Hello to everyone,
I have a r56 jcw we have changed the maf sensor because of chek engine code and the fuel pump because the car worked lean, also we check the turbo and is all fine... But i had notice tha the car can't hold pressure to 1-1.1 bar pressure and after 1.3 overboost the pressure fall to 0.8 bar
Thank you in advance