the boost adjuster is nothing special. It is a just a pressure relief valve used to bleed off the pressure for the wastegate cannister. I can get you a brand name/part# but any surplus stores can help you as they have them in bushel baskets. This is not the only one way to raise boost. The forum has posted several alternatives. I am using this because it works. I am also experimenting with the wastegate actuator rod mod combined with a spring between the cannister and the wastegate.
When you close or lift off the throttle (between shifts) from high boost, built up pressure in the intake goes in the reverse direction to the turbo while the turbo impeller is spinning at very high RPMs. The BOV serves 2 purposes. It relieves (blows off) that pressure preventing eventual turbo damage and as a result of this pressure not hitting the turbo, the turbo stays spooled up, eliminating lag when you stomp on the throttle again.
Factory setups feed the relieved pressure back into the air intake. Aftermarkets and how I have it setup, relieves the pressure to the atmosphere which makes the hissing that is heard.