Using the ScanGauge II helped improve my milage slightly, from my average 27mpg to 28mpg

But the backlighting can be hard to read when you're driving, so I switched from blue to green, which made the screen much easier and faster to read the gauge data. Finally there's a way to tell how hot the engine (the coolant running through it) gets while driving. I could see how intake air gets cooler once the car is in movement, so the benefits of a CAI over an SRI get a bit less pronounced. I'm very happy with it so far.