If the engine has dropped then most likely mounts are shot certainly don't want to be driving it like it, correct it is a Amal valve essentialy electronic boost control. The third pipe goes to airbox if you have one otherwise just vents to atmosphere.

If it's standard breather it goes to a kidney box which can be removed to clean etc on a Cosworth but can't be sure on your car, if it's aftermarket I.E Bailey tip up and empty out some even have a indicator on the side so you can tell. You have two connections on the breather both come from block but can vary, both should connect to breather.

Martin