Using your Nostrum High Pressure Fuel Pump is easy. Just follow the installation instructions that come with it to fit it into your 2015 - 2021 Subaru WRX. Make sure to use the right tools and take your time during the installation process. When it comes to fuel, you can use ethanol blends up to E100, but always ensure the fuel is clean and free from contaminants. As for maintenance, keep an eye on the pump's performance. If you notice any decrease in power or strange noises, it might be time to check the pump. Also, it's a good idea to have it inspected by a professional periodically. Remember, this pump has been dynamically tested, so it's built to last, but proper care will ensure it serves you well for a long time.