From what I understand...AirREX is only selling them as kits because the fittings have to be changed out for other management systems and is not optimal for production. The AirREX management system works great. It may not be as fancy looking as some others but for the person who wants a kit that is simple to install and works great with warranty you can't go wrong with them
We are the same way at STILLEN. We don't sell parts of our AP Big Brake Kits or Part of our Supercharger kits. There is always a market for the guys who like to piece things together, but as a company we like to be able to offer support and warranty for our kits and cannot help much when people customize everything (but we do see the appeal there for some people).