The Ford 4.6L/5.4L Modular 3V engines found in 2005-2010 Mustangs are all the rage. So the question on everyone's mind becomes, How can I further improve the performance of these powerful engines? The new COMP Cams® XFI VSR Ford 4.6L/5.4L Modular 3V (Valve Springs Required) Camshafts deliver a great power improvement over stock levels. These cams are the next step up from the COMP Cams® NSR (No Springs Required) Cams and represent a major upgrade in power production. When compared to the NSR, stock valve spring compatible cam series, the VSR cams offer a substantial power gain in the higher rpm ranges. To achieve this, a high-lift design that requires a COMP Cams® Beehive Valve Spring upgrade was created to maximize power within the limits of the OEM unmodified cam phasers. These new VSR camshafts are available for both naturally aspirated and supercharged engines, with two levels available in each series; one designed for maximizing mid-range power and torque, while the other maximizes top end horsepower.