Originally Posted by FuzzyRag
It's a pretty good bet that anytime anything claims to increase mpg and increase power at the same time, that it's just mythical advertising.
Not necessarily, if you increase efficiency then you can increase horse power. With this it takes less throttle to maintain or accelerate, thus less gas.
This only holds true if your driving habits are the exact same before and after, but we all know this never happens when you add a "power" mod. People always get in to the throttle more with an increase of power.