HellfighterZ

I'm planning on purchasing this system, but so far I have not do anything to my car completly stock, will installing this kit decrease/increase gas mileage or pretty much just stay the same. I do alot of highway driving and short drive to work, an I'm pretty happy with the mileage I'm getting , I plan on getting exhuast and HFCs in the future but I'm opting for intakes first.

I just wanna know what you guys/gals have experienced after installing you intakes. Gas mileage wise