Pypes now makes some like these too. The Dynomax patent expired on the Flow Directors and PYPES now uses them. Theirs also work pretty well.

So what does Pypes call them?
When i bought my Pypes kit the guy recomended Street Pro's in Stainless, so that's what I got. I have not installed their system yet. Grabbed the 2.5" X pipe system - and Doug's Header