Hi, this is my first time posting in a forum so please be patient with me. I have a 2011 Chrysler 300C with a 5.7 Hemi. It keeps fouling the same 2 plugs on the #7 cylinder. My husband replaced the coil pack and plugs and it ran fine for 2 weeks and then fouled them again. This time he just replaced the plugs and again, ran fine for 2 weeks and fouled them again. Why is this happening and how do we fix it? Could it have something to do with the fact that the catalytic converter is plugged and occasionally belches clouds of smoke?