Yep those injector lines are a good candidate for picking up crud. You will be surprised how small a piece can cause trouble (just try to see the injector hole). When you take on a job like this it has to be clean, very very clean. If you are lucky it will be a big enough piece to come out by just dumping the injector upside down. If you are not lucky the injector will have to be taken apart and cleaned. In the injector world a grain of sand would be like trying to swallow a watermelon.
Good Luck