I'm helping my dad on his car and its an 03 Pontiac Bonneville SSEI with the 3.8 Supercharged. I am only talking to him on the phone. But One day it just started running rough while at a traffic light. Then After I parked it, it wouldnt start and when it did it ran real rough then died. Now when it is a first start being cold it runs great and idle and revs up fine. But after a couple minutes it just dies. I checked fuel pressure while it was idling and it has perfect fuel pressure even until it dies. But the whole time its idling it has a real bad exhaust smell. Like rotten eggs. Also there are no codes and while it was idling once it reached 195 it died. I'm thinking its either the O2 sensors, or a Coolant Temp Sensor. I was also thinking maybe its a bad coil pack causing a cylinder misfire which would cause alot of unburned fuel to mess up the cat causing the smell. Seems odd that this is still no check engine light for anything. If it was a plugged exhaust but why would it take 10 minutes before it would cut off? Any help would greatly be appriciated.