Header Science: Step vs. Merge

We all know there's invisible voodoo that can make or rob power in an exhaust system. The guys explore the merits of stepped headers, whose primaries step up in diameter, and merge collectors, which create an intentional restriction in the collector, against good old-fashioned, no-frills headers. Do the frequency-tuning claims of the steps and the velocity-enhancing merges make a difference to your motor? Absolutely!