Hi

"The engine was running perfect with no signs of any problems, then in a split second, it died."

This sounds like a classic 740 symtom of a bad Hall Sensor. When it starts to go bad, engine heat will push it over its working resitance limit and poof! Your brick conks out in mid flight. Often when the car cools down it will restart and die again as it heats up. The fix is a new or reconditioned distributor that is already fitted with a new (delicate, and tricky to install by itself) Hall sensor.
I'm not sure if your '90 uses the hall sensor or something a little different.
Check the faq section and read about Hall sensor failures.
One way I'm told to tell is to look at your rpm guage as you are cranking the engine in a no start situation. If the needle jumps as you crank, you are getting a pulse from you distributor. If not, suspect a bad hall sensor.
The strange part about your post is you say it only idles. Do you mean if you start it up and give it any gas at all it dies? Or you can floor the pedal and it just sits there idleing along? I think if the TPS switch is broken it should cause the computer to run your idle high.. about 1500RPM, to compensate for the failed Idle control circuit. If your AMM had a catostrophic failure, the car should still be driveable, the computer meters enough fuel in this situation to allow you to limp home in slow motion.
Hope this help a little bit.

740man