After building a few of these kits and my own dual stage kit, I cant imagine why anyone would do a controller kit other then the Aquamist kit’s HSV. The HSV is the best solution hands down. You get a consistent % of liquid to fuel ratio all the way through the rpm range. I don’t see any other controllers doing this anywhere close to this well. I have yet to get just the HSV myself but Richard posted a diagram of how to implement one into a system with a Shurflo pump. You can get great results with a cheaper simpler kit just using (BPS) to start flow, then a controller based kit.