there is a 02 marking on the plug part, then, its hard to see but there is also 2 letters next to the plug part on each one and each are different, one injector has the markings jk on one side and jc on the other, on injector 2 it has markings jf and jb on injector 3 it has am and jd... at the moment can't find injector 4 but im sure it has similar markings.