The intake system of your car while effective as stock is hardly up to the task of supporting higher horsepower and performance upgrades. It is important to remove as much resistance while maintaining the integrity of your filtration system and allowing for smooth air flow. There are a variety of kits available ranging from ones that just swap the stock filter with a more performance based one to those that replace all the stock intake piping and air box. They all allow for more air to be fed to the engine and with them installed your engine will feel more responsive. It is important to remember that more air in the intake will not only increase performance but also lean your mixture out. Therefore it is good to accompany an intake kit with an AFC or other engine management that will allow for setting the mixture of you car to match the increased air intake. RHDJapan recommends Trust Greddy Airinx and HKS Super Reloaded suction kits.