What were the headers worth where the tire meets the tarmac? In torque, output was up by as much as 34 lb-ft with the biggest gains in the upper midrange at around 4,000 rpm. Peak torque, which was recorded at 4,600 rpm in the stock Hemi, moved up by 11 lb-ft. The largest gain in horsepower was again in the midrange, boosting output at 4,000 rpm by 28 hp and adding 9 hp to the peak output, recorded at 5,400 rpm. These results were through an otherwise dead-stock truck pushing through the stock single-exhaust system. These tubes definitely work.