Using the Upgrade from Cobb Old Ethanol Kit to NexGen Flex Fuel Sensor Kit is straightforward. First, make sure your vehicle is a 2015 - 2021 Subaru STI, including the 2018 STI Type RA. If you already have the previous Cobb Flex Fuel setup installed, you're good to go. Mount the NexGen Flex Fuel Module on the passenger - side strut tower. Then, use the provided plug - and - play wiring harness to connect your existing Cobb Ethanol Content Sensor to the new module. When it comes to maintenance, regularly check the wiring and connectors for any signs of wear or damage. And remember, this kit doesn't work with factory fuel rails and fuel lines. If you need them, you can buy COBB's fuel rails and lines separately. Always follow the safety procedures when working on your vehicle's fuel system.