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The K&N Engineering knn57S-2003 Performance Air Intake System is designed for select BMW 335i applications from 2007 through 2009, including the 2009 BMW 335i xDrive. It replaces the restrictive factory air filter and air intake housing with a fully enclosed, injection-molded air box designed to reduce airflow restriction and help smooth and straighten incoming air.
By allowing the engine to draw in more air than the factory filter assembly, this K&N performance airbox is designed to support increased usable power and acceleration throughout the engine’s RPM range. The air box connects to the factory air intake hose and uses the previous air box space for installation.
A removable lid provides access to the filter when cleaning is required, while the installation is described as relatively easy using commonly available tools. The system is backed by K&N’s No-Hassle Lifetime Limited Warranty. The associated products listed for this system are the RU-5293 Universal Air Filter and the 99-5000 Filter Care Service Kit Aerosol.
This product is not CARB approved. Review vehicle application information and applicable emissions requirements before installation.
Features:
Order Processing
All orders are processed and shipped within 24 hours of purchase (excluding weekends and holidays).
Orders placed after 3:00 PM EST may ship the following business day.
Shipping Methods
Customers select their preferred shipping method and speed at checkout.
Shipping times are determined by the carrier and cannot be guaranteed by us.
Tracking information will be provided once your order has shipped.
Shipping Coverage
If your package arrives damaged, please notify the delivery driver immediately and contact the shipping carrier to file a claim.
You must report any missing or damaged items within 14 days of delivery.
After this time, we cannot be held responsible for lost or damaged items.
Return Window
You have 30 days from the date of delivery to request a return.
After 30 days, we are unable to accept returns, exchanges, or refund requests.
Eligibility
Items must be returned in their original condition—unused, unwashed, and with all tags and packaging intact.
Certain products may not be eligible for return (e.g., special-order items, customized products, or perishable goods).
Items that have been altered, installed, or modified cannot be returned.
Return Process
Contact our Customer Support team to request a Return Authorization (RMA) before sending items back.
Once your return is approved, you’ll receive instructions on where to send the product.
Customers are responsible for return shipping costs unless the item was defective or incorrect.
Refunds
Refunds are issued to the original payment method once the returned item has been received and inspected.
Please allow 5–10 business days for the refund to appear on your account.
In some cases, a restocking fee may apply (if applicable, this will be disclosed during your return authorization).
