supergeorgy

Hello I have a 2002 Audi tt quattro and I have been having a problem where every time I give full throttle once I hit 4 thousand rpm's all powere being made from the turbo cuts out and I can hear the pressure air coming from the turbo being force back in making that famous cho cho sound which I know is very bad for the turbo. I have installed a aftermarket installed a Borla full cat back exhaust, a neuspeed cold air intake, and a forge 008 DV and I have already changed the spring in the DV to a higher psi spring which helped a tiny bit but still had the problem just as bad does anyone know what or why I'm having this problem. Any suggestions would be greatly appreciated.