Does an increase in airflow (intake or exhaust runner) move peak torque up or down the RPM band?

oldkimmer said

The 470 in my race car picked up a little on the low end when I put on header extensions. Kim

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I don't doubt that. Most collectors are way too short. That's why some guys add mufflers and go quicker. They needed the collector length. And some go quicker with exhaust because they have traction issues and the loss of HP from mufflers gets the car to hook.