Like always you kind of twist the argument. I didn't say that horsepower can't be gained by getting different headers. Just the fact remains that the Doug's headers have not bigger tubes than the summit. The inner diameter. They may be different lengths or something like that and may produce a little more horsepower who knows?...
You get people like 318 has valves that will fly puts Doug's headers on a maxi van 360... And I put cheap Summit headers on a dual quad Stroker...