Not sure what's in the 2007 F550? But it's pretty underpowered for a Huge V8 Turbocharged Diesel! .... And uses Coolant.
2008 6.4's are supose to be alot better I heard?
2008 F150 FX4 SCAB : BLUE STREAK
She's gone but never forgotten! Replaced with a blown:
2008 F150 FX4 SCREW : SILVER BULLET