AEM 19 21 Subaru WRX STI 2.5L H4 Cold Air Intake System Evasive Motorsports: HKS Super Flow Intake Subaru WRX FA20 15 21 Grimmspeed StealthBox Cold Air Intake BLACK Subaru WRX VA 15 21 AEM Cold Air Intake Subaru WRX STi 2.5L H4 (19 20) Gunmetal Gray Finis K&N Cold Air Intake Subaru WRX STI 2.5L (2015 2017) [Typhoon Kit] 69 8. The HKS Cold Air Intake Box Kit VAB for 15 21 Subaru WRX STi 4D is a highly effective intake system designed for HKS Racing Suction to improve the flow of cold and oxygen dense air to the engine. NOTES Cold Air Intake Box only. Required Racing Suction (70020 AF108) for installation APPLICATIONS Subaru WRX STi 4D (2015, 2016, 2017, 2018, 2019, 2021) FEATURES Designed as an upgrade item exclusively for racing suction. By completely separating the engine compartment from the air cleaner, fresh air can be constantly introduced for stable performance. The cleaner box cover and duct cover are made of carbon fiber and manufactured by the vacuum infusion method, which is almost as light and strong as the autoclave method. The surface of the carbon cloth is a 3k twill weave to dress up the engine bay. The cleaner box is made of fiberglass and individually created by skilled artisans using the hand layup method. The combination of matte carbon and black color makes the beautiful engine bay with exotic car vibes. It does not spoil the "open" sports sound that comes from the sound of air rushing into the intake. Compared the intake air temperature using WLTC mode on a chassis dynamometer that can control the room temperature regardless of environmental conditions. While maintaining the intake efficiency of the open type racing suction, the cold air intake can keep the intake air temperature stable and lower than that of the stock air cleaner. Cold air intake will supply cooler air to the turbocharger and greatly contribute to improved performance.