That is simply the boss for secondary squirters. Not used on any vacuum secondaries I've seen except the one posted by Treblig.
Worst case, if its really leaking (should see that by fuel level dropping when the engine is shut off) might have to take it apart and look.
Sometimes even simple things like this can be hard to figure out. See last post, where he figured out where the leak was coming from. 4412 has me stumped
