Yes Part 5 is the pipe.
The other 2 parts are dump valves, diverter valves, Blowoff valves are used to prevent compressor surge, a phenomenon that readily occurs when lifting off the throttle of an unvented, turbocharged engine. When the throttle plate on a turbocharged engine closes, the high pressure air in the intake system is trapped by the throttle and a pressure wave is forced back into the compressor. The compressor wheel slows rapidly and may even stall and the driver will notice a fluttering air sound. The rapid slowing or stalling stresses the turbo and imparts severe
turbo lag if the driver accelerates immediately after the surge event.
Mark