When I had my '05, I went to the dealer for an oil change, and my service advisor noticed I had put in a Fram Air Hog. I was advised to replace it or run the risk of having my nice 7/100,000 warranty voided. It seems, according to DC, that aftermarket filters increase the chance of drywashing the cylinders. To tell the truth, I never noticed a difference between stock and aftermarket anyway. I have a WIX stock filter in my '01 now, replacing the K&N that was in it, when I bought it. I cleaned a ton of black goop from my turbo inlet last weekend, confirming that the filter oil does muck up that area.