Can some explain to me, how they work? like, what part do they physically trigger? thanks, newbie to boosting.

 

You know how the W/G gets a boost signal from the manifold to trigger it? There's a fitting on the vacuum side of the W/G that gets hooked up to the EBC's solenoid that also sees boost. The EBC solenoid lets the boost pressure thru to the vacuum side of the W/G, keeping it closed(since both sides of the W/G are getting the same pressure, it stays closed) until boost reaches the level you've selected. Then the solenoid diverts boost pressure from the vacuum side of the W/G and bleeds it off, alowing the W/G to open and hold the boost level you've selected.

That's how my SSBC worked, anyway, until it got busted
I'm dumb, so feel free to correct me.