I recently thought I had a problem with the motor running lean to much but I figured it out. On my D16y8 is it possible since the engine is designed to run on the safe side of lean at idle that the computer would tell two injectors to run leaner than the rest? I just changed all 4 plugs and two came out the dark gray, one came out white/gray and the one closest to the timing belt came out mostly white with the gray at the very end. I have to idle down a 1000ft driveway then I shut it off so im wondering if the computer can do that. thank you

Edit: How do you know when an injector goes bad?