I had a K&N Panel Filter installed, 0 difference in performance, maybe a smidge louder if you really listen. Bought just a AirRaid CAI and noticed a pretty big difference in higher rpms due to the larger cone filter that brings in more air. Throttle response, and exhaust note changed in a good way also. $50 for 1 hp/tq compared to 10-15x the amount for $279!
The only way the modification will void your warranty is if the aftermarket component causes (could cause) the failure associated with a warranty claim.