(STAGE 2) Blower XFI™ SPR, XE272PH-13 Big Mid to Upper-RPM Power, Bolt-on Blowers
XFI Spring & 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 & phaser upgrade. Custom tuning required. Best with 3.90+ gears & 3000+ stall.