My last thoughts.....
For what the DV needs to do, I think the GFB is, at the very least, overkill. All the other DV's accomplish the task for far less money. It doesn't seem as though the GFB is going to do anything superior to what the others will do. The fact that the GFB incorporates an additional valve to vent air to the atmosphere under severe boost conditions is a vague engineering design - with the closed loop system of the Audi it is necessary to keep the air recirculated. Furthermore, there is no reference to how much psi is vented and how much is recirculated - I would assume they don't know.
Here is their words on the subject:
"First, your pressurized (boosted) air must escape both the inlet pipe and the intercooler (even high performance intercoolers), opening the piston and giving a loud "whoosh". Within seconds the pressure is evacuated from the inlet system allowing the Turbo to continue to spin and pump air through the valve. Even though the car is venting to atmosphere, a sufficient volume of air goes to inlet and passes through the air flow metering system, reducing hesitation (the lean Audi second) or backfire."
I don't like the Within seconds and a sufficient volume of air phrases. The first is oddly too long of a time frame, the second is extremely vague. That can be dangerous.
It sounds like it might be a consideration for those systems that are experimental and/or are producing massive boost, but it would have to be an outrageously high range for an experimental/massive boost system to benefit from this unit - and, not knowing what the psi values are for the valves, it would be an experimental gamble. Otherwise, it may very well be a dangerous application.