I have a 2001 mustang bullitt. It is all stock except for upr x-pipe w/o cats and an slp lm2 cat back. Anyways, I was downshifting while coming to a traffic light and it sounded like the engine was humming or siezing up. The rpms droped and the car stalled out. I started it back up and it ran fine. I was wondering if anyone has had this problem before. Could it have been caused by bad fuel or could it be something else? Also I have heard of the IAC stalling out cars, but never having the humming come with it. Any advice to fixing this problem would be greatly appreciated.