Not necessary but encouraged. I have a Fore inline fuel filter on mine. I spoke with several tuners and they recommended it as a good idea. Lots of people don't do it but if you plan to run E85, it helps keep those pricey injectors clean. It doesn't cost much to change your fuel filter annually compared to having your injectors serviced, cleaned and checked. After I paid almost $200 for my ID 1300x2 injectors to be serviced after 2 years of use, I realized it was a lot cheaper to use a fuel filter and swap the removable media every year.