I just did some diggin into my S2 to find a similar problem. In my car it looks like the stock hose clamp goes kind of egg-shaped, and could allow a leak. I replaced the lower stock clamp with 2 aftermarket clamps, and the upper with one, it seems to smell better now. I think I still have a good likely causes link:
http://www.clarks-garage.com/shop-manual/ts-03.htm#fuel-smell