I'm not sure where this information is coming from. Here are the basics:Originally Posted by Slide
You get in the throttle, the wastegate closes down, eliminating the bypass into the exhaust (via the DP) and thus, increasing boost. If you continue with the throttle down, the wastegate starts to open, disharging into the dp and thus lowering boost. If you think of the wastegate as an adjustable throttling bypass valve it works perfect. When it is open, less boost. When it is closed, more boost. The size and configuration of the DP helps to determine the flow and mix, but ultimately has very little to do with boost control. It essentially acts as a controllable backpressure regualator for the exhaust flow powering the turbine.
Also, the DP has nothing to do with boost creep. It has everything to do with freeing up your exhaust flow, which in turn allows more air intake and thus fuel intake, and thus faster boost response if tuned for it. It also supports lower EGT temps.
As I said earlier, there are only 3 methods that can control this. A DP is not one of them to the best of my knowledge, unless you are including a HF cat in it.