This has already been discussed before:  please do a search on this forum, but short answer is it’s snake oil.  

Not the first time gadgets like that have come up here. Total snake oil that might even cause damage depending on just how badly it's designed and made.

Think about it logically. Manufacturers are going to practically insane lengths to meet increasingly draconian government regulations. Complex and expensive systems of dubious merit are included in new cars to eke out a fraction of a mile more per gallon of fuel. Don't you think that if a "magical" gadget like the EcoTune actually worked that manufacturers would be falling all over themselves to build it in at the factory?

That stuff is all smoke and mirrors. Those plug-in things that claim to re-tune your car for better gas mileage don't do anything or make it worse. The engineers who designed your car already designed and programmed it to be as fuel efficient as possible and still deliver expected power. Auto manufacturers face financial penalties if their cars don't meet federal fuel consumption regulations. If you boost power, you lose fuel economy. If you boost fuel economy, you lose power.

there are endless posts about this garbage on our forum. Please stop wasting our time.