I cam out of my house this morning and noticed a large wet spot under
the back of my car.  Upon investigation it appears to be a fuel leak
from a black vented box that is immediately behind the driver side
rear tire and connected directly beside the gas tank.  there are 2
hoses that appear to be fuel hoses going into the forward end of this
box.  I disconnected two mounting nuts and looked inside but it is an
enclosed box mounted inside the casing.  I can't find any info on the
net or any illustrated parts lists.  Can anyone give me an idea what
this box is and why it might be leaking fuel?

I did fill up my tank last night and I "topped" it off to round the
price.  My car also parks on a fairly decent slope in my drive way
rear end first.

Thanks for any advice!