The one thing I have learned is that the TurboXS HPBC is a combination ball and spring boost controller on the course adjust and a bleeder valve on the fine adjust. Just like the stock boost control solenoid is a bleeder valve, all bleeder type manual boost controllers tend to have boost fall off in the upper RPM's. With intelligent control of a solenoid via some of the reflash systems you can maintain boost on a bleeder....but a "dumb" bleeder (stock ECU or manual controller) don't work worth a damn! I am currently using the course adjust on the TurboXS HPBC alone without any input from the fine adjust and it holds boost just fine till redline. What sucks about this is the course adjust is about 1 psi for ever 1/4 turn of the adjustment! Very hard to get it set just right. I don't recommend the TurboXS HPBC to anyone, just get a Halman and you will be a lot happier 
Keith
Keith