Sounds like a possible ground problem for the tail light? I don't have fog lamps, so I cannot say how they come out. I swapped in clear signals tho, and if I remember correctly, the plastics under the signals were just snap-ins, I'm not sure if the fogs trim are snap-ins as well or not. If you have JDM fogs, I'm pretty sure they're not snap-in, since there is no trim.