vents just used to go to the top of the rear screen, or boot seal aperture......... if that makes sense
never down, as if it starts to leak graviry will take over and empty it, like a syphoning effect

http://www.merlinmotorsport.co.uk/p3...duct_info.html

or

http://www.ebay.co.uk/itm/Fuel-Tank-...d=351958128819