Had this problem 5 to 6 times yesterday thought I will document it here since this can be a common problem, when slowing down in traffic the car just dies without any warning light on the dash. All the electrical systems like Stereo,AC Blower etc will be working fine at the time. Also when tried to restart the car it will start in the first crank. Some thing to do with Fuel pump, relays etc. Only error code recorded was a P249 which o think is not related..

Worth getting the car cleared of codes and then rescan to see if it has stored any error codes to investigate. I did have a similar issue and mine turned out to be the fuel pump, but I think this is more to the point that I was running a stage 2 and didn't bother to upgrade it.

Thanks Dean... i cleaner the battery terminals and the auxiliary supply terminals and drove the car close to 80miles today she was all fine. Will check again for any codes. Fuel pump is most likely to be the culprit for a 100K mile car. Will keep everyone posted.