"Box" behind fuel tank??

[72CutlassS]

I had my '05 Tahoe on the lift the other day after my wife thought she might be smelling gas. (It might be the strong rubber smell off of some new floor mats.) While on the lift, I did see some moisture around this "box" mounted behind the fuel tank. (It was hard to tell if it was gas or grease sling from the driveshaft.) It has fuel lines running in and out of it.
My first question is: What is it?
My second question is: Do these go bad or develop cracks frequently?

With gas prices climbing again, I don't want to be losing any. Not to mention the safety issues associated with it.

Thanks

 

[72CutlassS]

Bump....anybody??

 

[afpj]

Hope this thread answers your question...good pics and info about EVAP system:

http://www.tahoeyukonforum.com/forum/showthread.php?t=16989&page=4