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Na vs. Kenne Bell Supercharged 4.6L four-valve Motor (9.2 psi and 19.9 psi) - We began this adventure by running the modified '03 Cobra 4.6 in normally aspirated trim. This was done both to establish a baseline and allow some break-in time for the rings and bearings. The NA version produced 416 hp and 393 lb-ft of torque. While this was less than expected, we installed the Kenne Bell blower and ran it at 9.2 psi where the engine produced 570 hp and 488 lb-ft of torque. Stepping things up to 19.9 psi with a 3.75-inch blower pulley brought the peak power to 767 hp and 698 lb-ft of torque.