K&N Air Filter
The freer-flowing, cleanable K&N filter may add slightly better airflow than the stock paper element, but not so much that you could feel it. The main benefit I discovered was that the air flowing in through the hood scoop attracted not only plenty of dirt but, strangely, lots of bees. The hood does have a very effective baffle to keep out rain, but make no mistake, this intake will pick up more crud than a conventional induction system.
This is the same filter that fits the LT1 Corvettes so availability isn't an issue.