4 With our base of 551 rwhp and 474 lb-ft of torque in place, we spun the rollers again—this time with the 3.125-inch pulley on the blower. The smaller pulley made about 9 psi of boost (2 over our 7-psi baseline), which helped our GT make 583 rwhp and 498 lb-ft of torque. A gain of 32 rwhp and 24 lb-ft is definitely solid, but we wanted more. The 3.000-inch pulley made an addition pound of boost over the 3.125-inch pulley, which equated to 595 rwhp and 519 lb-ft of torque at 10 psi. This gave us a gain of 44 rwhp and 45 lb-ft of torque over the 3.337-inch pulley, and a gain of 12 rwhp and 21 lb-ft over the 3.125-inch pulley.