Ok, I've gotten to the point where I've push out a few more childhood memories so that means I have room for more stuff! I'm curious to know if anyone feels like educating those that may not know (like me!) about vacuum lines in regards to GM trucks. Questions I'm curious about are things like.. What do vacuum lines do, in general? How many lines are we talking about here? Are they something that can be changed out while doing maintenance in order to prevent future troubles? What is the reasoning behind checking for leaks by spraying something like an aerosol? Are vacuum lines all pretty much part of one system, or do several different systems use vacuum lines? Anything else we should all know about vacuum lines?