You're probably right. I'm not saying there isn't ANY difference but discernible from one day to the other? Not likely unless you sat there for hours just listening to these things. With different tube lengths from different runners from one header to the other, sure there's going to be a potential pitch or thrum change. But generally, if you were to put SW long tubes on your car and an ARH car came zooming by as well, you probably wouldn't be able to tell in any passing. This isn't like the difference between mufflers where their sole purpose is to augment sound into a very specific profile where headers and manifolds are very much part of the fundamental profile as a whole along with firing order, firing angle, intake design, head design, and compression.
