There are a bunch of brands coming out with their versions. With dyno sheets of hp numbers here is whom I know of so far:
Supersprint, Tubi, Gembella, Milltek, Sportec, Techart, AWE, 9ff, Ruf, B&B, Fabspeed. I might have missed a few, that is only off the top of my head. I'm sure in the future, you will see others like Eisenmann, Magnaflow,
Borla, Cargraphics to name a few.