1fastkia is right, there is not a perfomance increase, and the price for it is NOT worth it. Now I notice that it will only help if you ahve alot of bends in your intake pipes, but fi you have a short ram, then please don't put it in (same goes with a CAI) since its just gonna mess up your intake, the reason why I know this is because I made an equivelant out of some extra sheet aluminum just to see what it would do, I tried it in my short-ram and tried it in the stock piping (which has 2 90* bends.) It helped the stock piping since the bends severely restricted airflow and I felt a little more low end performance (mid and high were negligable) but since short rams have the least amount of bends and have softer bends as well as a smooth inside, it will just get in the way. Besides, your money is better going somewhere else that will ACTUALLY MAKE A DIFFERENCE. for about 50 to 75 bucks, its crap, and if you want it so bad, you can make it yourself for about 10 to 20 bucks with some sheet metal. In the end, its NOT worth the wasted cash and will not help gas milage or performance, its just a gimmic.
Besides, most of us that modify our cars will end up putting in a better intake system, so its better to go that route.
EDIT: Stupid me! I forgot to mention something, this "device" is not a good idea to install, why? Because it goes between the intake manifold and the sensor, so the air between there is UNMEASURED and thus makes your engine run Lean which is good for fuel econimy but BAD for engine power and performance.
Read the 9th post by Ghost hunter to get a better idea. Best avoid it if you want your engine to last long and be in reliable condition.