Big power gains in mid to upper RPM range
XFI Spring and Phaser Mods Required Blower 237/248 Hydraulic Roller Finger Follower Cams for Ford 4.6/5.4L Modular 3V. Big power gains in mid to upper-RPM range for bolt-on blowers with high boost. Rough idle, Solid power gains above 4900 RPM, requires spring and phaser upgrade. Custom tuning required. Best with 3.90+ Gears and 3000+ Stall.
