Hi mate, seems like you have a simillar problem to one of the ones I have, I have two threads running in Tech at the mo (lucky old me) and one of them has the very same symptons as yours.
I'm now 95% sure it is the EGCV actuator, which sits under the 1st turbo, it is an actuator which moves a large'ish ceramic valve on the exhaust side of the 2nd turbo, and if this valve is stuck shut you dont get anything from the 2nd turbo, all the boost is dumped. This is what I've been told and also sounds right when I read all the tech stuff.
I only said 95% sure because my second problem has surpassed this one.
Best of luck, keep us informed.
Bob.