I removed mine... I dont smell any gas fumes. Do cars modified with fuel cells have a fuel purge and charcoal cannister? No... Gas mileage? wtf. Do you realize the VERY SMALL AMMOUNT of gas that actually would escape from there? I replaced mine with a small pressure release valve located at the tank itself... so that as the gas sloshes around it releases pressure on its own so I dont have a time bomb behind me...
not to mention the solenoid, the box itself, the wiring, and all the tubing weighs a good ammount.
If you want... you can remove it without any problems. Some people argue that it "helps with the air/fuel mixture"... but since the gas pressure is never a constant level, how in the heck could it properly and consistantly help with an air/fuel mixture?
One bad thing about removing it... you'll have to find a smog guy who doesnt really care about visual inspections... I currently dont have a pcv valve (been replaced by breather), EGR valve (deleted), or fuel purge solenoid and charcoal cannister. Anything having to do with smog has been removed.