If the IAC doesnt fix the issue, I had the exact same problem. Driving along and the VX would just die. Turn the key and it would start back up. Mine ended up being the fuel pressure regulator. There are numerous threads here detailing the replacement process. It's at the rear of the engine, but up high. The hardest part is reaching it, and you would need a shortened allen head to get to it. I believe it's about a 50 dollar part.
All that said, hopefully you'll have your issue resolved with the IAC. Best of luck!