Price: $449
When it comes to maximum airflow, there isn't a company that knows more about it than K&N. It has taken its knowledge of high-flow air filters another step further by making an intake system for the Yamaha YFZ450. This system replaces the stock airbox and intake tube with a rotomolded intake tube and powdercoated aluminum airbox/heat shield and uses an oversize K&N high-flow air filter. It claims that using this system can give you an increase in power by over 4 horsepower. Each kit comes with everything you need and detailed installation instructions to make your upgrade a snap. Just like all of its products, the intake kit is covered by the K&N limited warranty for one year.
K&N: www.knfilters.com; 951/826-4000