The AEM 21-478WR cold air intake replaces the restrictive factory air filter and intake housing on specific Subaru WRX and WRX STI models with a system engineered, tuned, and dyno-tested for real gains in horsepower and torque. Air is drawn through an oversized AEM Dryflow synthetic washable filter mounted in the stock air box location and shielded from underhood heat, while mandrel-bent aluminum tubing with a textured red powder coat finish routes air to the throttle body. The system retains the factory mass air flow sensor and other emissions hardware for a clean installation with common hand tools.
Installation InstructionsVehicle Applications Sheet
Specifications:
- Filter Type: AEM Dryflow oil-free, washable, reusable synthetic media (cleanable up to 100,000 miles between services)
- Filter Shape: Cylinder
- Tube Material: Mandrel-bent aluminum
- Finish: Textured red powder coat
- Warranty: AEM Lifetime Limited Warranty
- Emissions Note: Some AEM air intakes are not legal for sale or use in California and other states adopting California emission standards, while others are 50-state legal; check vehicle-specific legal status before purchase.
- Part Number: 21-478WR
Vehicle Applications
- 2011 Subaru Impreza 2.5i
- 2011 Subaru Impreza 2.5i Premium
- 2011 Subaru Impreza Outback Sport
- 2008 Subaru Impreza WRX
- 2009 Subaru Impreza WRX
- 2010 Subaru Impreza WRX
- 2011 Subaru Impreza WRX
- 2012 Subaru Impreza WRX
- 2013 Subaru Impreza WRX
- 2014 Subaru Impreza WRX
- 2010 Subaru Impreza WRX Limited
- 2011 Subaru Impreza WRX Limited
- 2012 Subaru Impreza WRX Limited
- 2013 Subaru Impreza WRX Limited
- 2014 Subaru Impreza WRX Limited
- 2009 Subaru Impreza WRX Premium
- 2010 Subaru Impreza WRX Premium
- 2011 Subaru Impreza WRX Premium
- 2012 Subaru Impreza WRX Premium
- 2013 Subaru Impreza WRX Premium
- 2014 Subaru Impreza WRX Premium
- 2008 Subaru Impreza WRX STI
- 2009 Subaru Impreza WRX STI
- 2010 Subaru Impreza WRX STI
- 2011 Subaru Impreza WRX STI
- 2012 Subaru Impreza WRX STI
- 2013 Subaru Impreza WRX STI
- 2014 Subaru Impreza WRX STI
- 2011 Subaru Impreza WRX STI Limited
- 2012 Subaru Impreza WRX STI Limited
- 2013 Subaru Impreza WRX STI Limited
- 2014 Subaru Impreza WRX STI Limited
- 2010 Subaru Impreza WRX STI Special Edition
FAQ
What years of Subaru WRX and WRX STI fit the AEM 21-478WR intake?
The AEM 21-478WR fits 2008-2014 Subaru Impreza WRX and WRX STI, including Limited, Premium, and Special Edition trims, plus the 2011 Subaru Impreza 2.5i and Outback Sport.
Is the filter washable and reusable?
Yes. The 21-478WR uses AEM's oil-free Dryflow synthetic filter media, which can be cleaned and reused for up to 100,000 miles between services depending on driving conditions.
Is this intake legal in California?
Some AEM air intakes are not legal for sale or use in California and other states that follow California emission standards while others are 50-state legal; confirm the legal status for a specific vehicle before installing.