'98 4Runner performance mods

Just bought a '98 4Runner limited with 80,000 on it...seems to be at a lot of it's service intervals, give or take a few thousand miles. First of all, saw that the air filter is dirty, anyone have a K&N cone air filter, and where do you get them and how much$$$ What are some other performance mods one can do without supercharging? Any help is appreciated, I love this new 4Runner. Please e-mail me at hugearms34@hotmail.com. Thanks, Eric