Yup, I keep all the fuel injector lines for the 6.4 and 6.7 Ford diesels in stock because they are not supposed to be re-used. Same as the common high pressure lines on the EcoBoost engines. People get irrationally angry having to buy extra parts, but when the shop manual says it must be replaced, its not like they have a valid argument.High pressure fuel line connections on 30,000+ psi diesel fuel systems are metal on metal. Sometimes can be a pain to seal up if there are any imperfections on the mating surfaces.