i bought a device that makes the air to fuel mixture “lean”. i installed it on my 2007 corolla. the car runs an average of 130 miles a day on regular Los Angeles traffic. (stop and go on rush hours and 70mph at night). i am testing out the device if it would save me fuel consumption but my concern is will it cause any damage? so far everything is running smoothly except for the “engine check light” being on. i assume that it is because the device is working and that the sensor picked up on the “abnormal” air to fuel ratio. please advice.

for specifications of the device, i bought it online at “onegassaver.com”