I recently started feeling a small miss when driving my wife's 04 navi. I thought it might be bad gas because on my way home today it started running really rough. I pulled the codes and got p0358, 356, 355, 354. The check engine light never came on either. I put some heat in the tank and drove a little bit. It seemed a little better but still running pretty rough. I was reading about bad ecu's and i can't imagine 4 coils going bad within a couple days. Any ideas on where to start?