Flex fuel on the FA20 is one of those mods where half the community swears it's the best dollar-per-horsepower upgrade you can do, and the other half says you're dumping money into a platform that doesn't reward it without a full supporting mod list. The E85 crowd will tell you the knock resistance alone changes the entire tuning window — cooler intake temps, more timing, and real gains on a motor that's otherwise pretty tapped out on 93. And honestly, they're not wrong. But here's where it gets spicy. If you're not already on a quality header, a protune, and ideally an oil cooler, that flex fuel kit is basically a $500 ethanol content sensor waiting for you to catch up. And depending on your area, consistent E85 availability is a real problem nobody talks about until they're hunting for a station at half a tank. So which side are you on — flex fuel early and build around it, or build the platform first and add E85 as the finishing touch? Save this before you buy the wrong setup. #T...