In the dyno picture above, we installed this manifold on a stock motor 6.1L 300C for testing. The test was done back to back, same day. Stock intake pull was done first, then the intake was swapped right there on the dyno immediately after. The Mackbuilt intake was tested immediately upon install, with the only tuning changes being fuel correction to maintain proper air/fuel ratio with the added airflow of the upgraded intake manifold. Notice the midrange gain of 25whp!
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