I have a friend who has a 2001 SSEI and awhile back his supercharger belt broke, He had it replaced but ever since the car will randomly die. It could be at 60mph or at a stop light. Sometimes it starts right up and sometimes it takes a couple of minutes?
I believe it was the IGN1 fuse in the underhood fusebox that was the problem. Pull the fuse and push the connections in the block closer together to see if that helps. While you're there, check the power connection going to the box, as well as the 3 screws inside. Then do the same in the rear fuse box under the seat..