S6 batty, 2nd turbo no boost!!
 

Hi, i have a s6 batty, engine is all standard. compression is mint. i have no boost from second turbo, checked 6 solenoids under manifold, wastegates, turbos are mint condition, no vacuum leaks, charge control actuator seems fine. first turbo is boosting 13psi which should be 8psi then switch to 2nd turbo but it isnt. under WOT at 4500rpm is looses first turbo boost and then sounds as though air is being forced out filter as though the 2nd turbo is spinning backward. I have spent a lot of time doing research and inspection and can't work out the fault. Any help would be appreciated. cheers