plugs wouldn't make it shut down. Run rough, yes. somewhere in the changing out or back to new injectors, I think there may be a problem. I would take it back to Buckhead if they were the last to touch it. Something has come apart or changed in the tune to make it that rich. I have similar mods and haven't had any problems since we went with a larger fuel pump. So, I would look at the mechanics that were last done, and at the tune.