The other way around... it open as manifold pressure increases to slow the exducer so you don't exceed a given target. Keeping it closed and you'll over boost very frequently and risk THOROUGHLY trashing something (see: turbo and/or engine).
The ONLY gain you see in not letting the waste gate open is that you will see less smooth of a drop off as you reach the target boost and the gate opens completely... Usually this presents as a surge... not too good for things but not a killer...
There's really nothing to be gained from what we've discussed here.. you're better off leaving it all alone. Go read up some more and then read up on boost controllers.
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