I Think It Depends On If The Modification Could Have Led To The Warranty Item. I Have A K&n Cai (off Road Version) On My F150. I Asked The Service Managers About It And They Know The Trucks Run Better But If It Is A Power Train Type Problem You Are Better Off Putting The Stock Air Intake On. He Said The Ford Rep Would Most Likely Void My Warranty If It Is On And He Sees It. It Is B.s. But It The Advantage That They Hold. Programmers, Turbos, Superchargers And Such Are Obvious To Me. Alot More Power And More Than Likely A Much Shorter Lifespan.

I Try To Keep All Of My Stock Stuff Just In Case, Exhaust And All. Also Being In California I Know I Will Need It For The Next Modified Exhaust/tinted Windows/no Front License Plate Ticket That Is A Standard In Socal.

I ALSO HAVE A 7 YEAR 100,000 MILE WARRANTY.