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8 With the Holley 670 in the same configuration as when run on the Cobra intake, we found the air/fuel ratio to be leaner with the Edelbrock Performer RPM--13:1 rather than 12.5:1. Here, the secondary jets get bumped up three sizes to No. 71s, to help hit the 12.5:1 number. Power and torque improved with the richer mixture, and the benefit of dyno tuning was obvious. Peak horsepower and torque from this combination was up 12.7 hp and 9.6 lb-ft over the Cobra.