[Shawn D.]

Originally Posted by 93Cobra#2771

"Stepped" headers have also become popular, as they start out big and then step down a bit in size to keep exhaust flow moving...

Actually, they increase in size at the step.

https://www.motorstate.com/TrendsInHeaderTechnology.htm

Another primary tube variation involves "step" headers. Used by drag and circle track racers alike to extract that last bit of horsepower, stepped primary tubes progressively increase in diameter, usually in 1/8" increments, from the flange to the collector. The "stepped" tubes help increase exhaust velocity for that last bit of added horsepower. Stepped headers are typically offered in single- and double-step versions; a single step header may have 1-7/8" to 2" primary tubes. A double step primary tube header may go from 1-7/8" to 2" to 2-1/8" between flange and collector.