the dealership can hook up the tech II and tell which injectors are faulty. If your going to replace the bad ones, replace them all. The dealership did my old mans at 115,00 but only did the 4 bad ones. now guess what? yep the other 4 are goin, and they wont cover it. Then my buddy took his in and they said you cant replace just the bad ones, have to do all 8. But they would be happy to do it for $4000. bunch of bullshit if you ask me. but i like the old LB7's, and if it were me i would fix it.