your turbo problem....
Hi, you are experiencing the same
problem that I have just had with my FR.
When you decellerate the waste gate opens to let out the pressure but sticks open, when you change gear and then apply the accelerator the turbo spins and all the boost goes out the waste gate as it is open.
My local dealer replaced the turbo under warranty even though the car is 4 years old, try your local dealer, you may be lucky enough to get a replacement as a sympathy claim, good luck!