When you put the collector headers against each other you see less of a difference. They might attributable to a change in the weather, as a small storm blew through during this portion of the test. The larger headers made 494 rwhp and 430 lb-ft of torque, while the smaller headers made 491 rwhp and 439 lb-ft of torque. The smaller headers made more horsepower and torque below 5,800 rpm, with as much as a 10hp difference. Both headers were equal until about 6,500, when the larger header pulled ahead, making as much as 8 hp and 7 lb-ft more.