yea its definitely doing something if its making the engine dip a bit when u turn the dial, but it could still be faulty. what boost controller do you have? try setting the fcd to 12, so its basically off, and try setting your boost controller to 0.8bar and get it to hold the boost steady once you have done that, then put the fcd to setting 10, and boost to 0.9 bar and get it to hold steady then finally setting 8, and 1bar boost remember to set the fuel pressure first if the car is hitting fuel cut even with the boost set at 0.8bar then its definitely a boost spike