I almost hate to even comment because it is dangerous. Mack says you must install a new one if you take one off. I changed a injector on mine myself, the flares looked good (not cracked) and reused the fuel line. I'm not sure about the torque on the nuts, I just went tight enough that I thought it would not leak but not so tight as to split the flare. I don't know which section of the manifold your working on but you may be able to change the gasket without taking the fuel lines off probably not. If you decide to reuse the line(s) make sure to check very carefully and very often at first for leaks, because as you can imagine, if fuel is spraying on a hot manifold it could turn very bad very fast. Good Luck
