That's part of the evaporative control system (ECS) that was put on cars sold in CA and maybe elsewhere. There are three or four small tubes that run up through it. One of the tubes is comes off the breather and runs back to the gas tank by the fuel line. Another tube in it comes from an vapor expansion chamber built into the top of the gas tank. Its all about capturing gas vapors so they don't become air pollution.
Well there you go.
