Why Schumacher didn't have a set to allow for Z Bar I have no idea. At the least I would think it's a set they would build with additional lead time without having anyone else involved. It is a Tri-Y header so it will be constricting versus a full tube header but plenty of people have made nice power with them. As for the other vendors, someone how the calculator has never made sense from a business standpoint to offer PS and Z Bar fitment......