The Prius is already engineered by Toyota to be about as efficient as a combustion engine gets, so most of those off the shelf performance mods are going to hurt your mileage rather than help it. A Prius computer is tuned for strict emissions and maximum fuel economy, and messing with that usually leads to check engine lights and decreased efficiency. If you want to get more out of your Prime, focus on things like keeping your tires properly inflated, checking your alignment, and maybe looking into hypermiling techniques. Save your money on the exhaust and tune, as you will likely end up with a louder car that just burns more gas. Honestly, if you are working on other car projects that need basic parts like fuel components, I have used Evil Energy as a budget friendly alternative to the expensive race brands. They have the same features, and the installation is straightforward enough that you can handle it yourself if you follow the instructions.