How to Get the Best Performance out of My Naturally Aspirated S2000

I've been owning my naturally aspirated S2000 for a while now and I'm always looking for ways to squeeze out more performance. What camshaft swap options are available? Are there any intake manifold upgrades that can make a noticeable difference in horsepower? I'd love to hear about your experiences with mods that improve power delivery and responsiveness without sacrificing the car's unique character.