You should not hear the pressure being relieved, unless you have a leak somewhere. The cars are normally released from factory na walang tunog na ganyan.

The best place to put tap the boost is on the intake manifold. When the turbo pushes air into it, dun siya pinakamalakas ang boost other than the turbo itself, before going into the engine for combustion.

After the air filter, it goes to the turbo. But after the turbo, it goes to the intake manifold, then to the intake plenums to each individual cylinder. From there out it goes to the exhaust, and back to the turbo to spin the turbine, and through the wastegate valve if ever man sumobra, then out the exhaust mismo.

http://www.beesandgoats.com/boostfaq/g2icturbo.html

Sample image of the wastegate attached to the turbo: