sorry to dig up this thread.
i had done an experiment to drive my car without any filter, and DID NOT experience noticable different in terms of power compared to the stock filter. one reason might be i had my AFR tuned which i don't know how much it affects this experiment. Therefore for my ride, i'll stick with the nissan's stock filter. i believe aftermarket filter which suppose to allow more air in will not work on my car and it'll protect my oxygen sensor most effectively.