K & N systems can be anything from a filter replacement only, to a complete housing AND filter.
Do they just 'sniff' the exhaust? There's no reason to think that emissions would necessarily be worse with a K & N filter, I think.
Emission Warranties on New Vehicles
THE MYTH: A manufacturer's new-vehicle warranty is automatically voided once an aftermarket part (non-original equipment) is installed.
THE TRUTH: Rarely does the use of aftermarket parts violate a new-vehicle warranty.
THE RULES: Federal law, (the Clean Air Act), requires two emissions warranties: a "defect" warranty and a "performance" warranty.
"Defect" warranties require the vehicle manufacturer to produce a vehicle which, at time of sale, is free of defects that prevent it from meeting required emissions levels for its useful life, as defined in the law.
"Performance" warranties require that vehicle manufacturer make repairs - at no cost to the owner - should a vehicle fail to meet certain levels of emissions performance during the warranty period. This period ranges from 2 years (or 24,000 miles) to 5 years (or 50,000 miles) for most parts, and up to 8 years (or 80,000 miles) for certain emission-controlled parts, specifically, the catalytic converter, the electronics emission-control unit and the on-board diagnostic device (check owner's manual for specifics on your vehicle).
Consumers are protected under a parts self-certification program administered by the Environmental Protection Agency (EPA).
If a parts maker self-certifies it's parts under this program, the vehicle manufacturer cannot void the emissions warranty even if the certified part fails and/or is directly responsible for the emissions warranty claim. In this situation, the vehicle manufacturer must arrange a settlement with the parts manufacturer, but the new vehicle warranty is not voided under the law.
If a parts maker chooses not to self-certify it's parts, the only case where a vehicle manufacturer can void the emissions warranty is if a non-certified aftermarket part is proven to be responsible for an emissions claim.