I've been following several recent low boost threads to try get to the bottom of mine - max 0.6bar on my MY93 WRX. Had a look at what I think is the boost solonoid (small cylinder bolted to the wing). There's a small pipe coming off the bottom, which connects to a largish black box which is just down the line from the airbox - don't know what it is. The connector which leaves this for the bottom of the solonoid had broken, and the pipe was haning loose. It has a circlip on the end, so it was obviously intended to be tight.
What is this for, and could it cause low boost?

cheers