Does anyone have the Eco-system fuel vapor enhancer. Do they work? If so what have been the results?

I put one on my Titan and went from avg 15 mpg to around 16.6 mpg now. On my trip to Jersey a while back I avg almost 19 mpg doing 75mph +.
I love it and think its great. Dont know how it works but we have a lot of guys at ClubTitan who love it.
M4ck