Originally Posted by Hobbymanbill
The only gain is made by removing restrictions (the air filter AND tubing) thats max gain until You can get unheated and unrestricted air into the engine. Anything below 200mph just doesn't add more than 2%. (On our engines thats 4hp) claims to the contrary are just that, claims !!! Turbo's and superchargers increase air flow by forcing air into the engine under pressure.Super duper Air filters and all the super tubing in the world won't change Flow dynamics. As much as you would like to believe it does won't change that.
I've talked to intake makers Neuspeed being close to me and yes they say about 5 hp maybe ,but changing the temperature as the cold air does it also increases power.Or helps the engine feel stronger.
The XFires intake gets VERY hot the way it sits over the engine and any improvement in cool air design would make it feel stronger.