3) Actual function is to purge the system like bleeding your brakes. To make sure that there is a constant feed of Nitrous and no air pockets. There are Nitrous Purge kits that are specially made to do so.
1987 N/A - CUSTOM 2.25" EXHAUST, TEST PIPE, PACESETTER HEADERS, COOL AIR INTAKE AND INTAKE MOD - BEST 1/4MILE TIME - 16.5 @ 86MPH