Enhance your YFZ450 '04 with the FMF PC IV 044224 Performance Exhaust. Designed for serious riders, this exhaust system features a U.S. Forestry approved spark arrestor and a revolutionary reverse cone megaphone design that offers versatile performance. Whether you're racing on closed courses or tackling off-road trails, the PC IV ensures you can customize your ride with its modular end cap system, allowing for optimal tuning tailored to your needs. Features: * Feature 1: U.S. Forestry approved spark arrestor: Ensures compliance for off-road use. * Feature 2: Megamax II design: Offers versatility for both closed course racing and off-road riding. * Feature 3: Modular end cap: Easily adjust the power band with various end caps for tailored performance. * Feature 4: Hi-Flo 2" end cap: Quick changes for enhanced performance; optional 1-3/4" end cap available. * Feature 5: Not for use in California on pollution controlled vehicles: Race use only with a waiver available.