1994 Pontiac Grand Am stalling

I'd have to do testing when the problem occurs. If it cranks good but won't start, have a helper crank it while you visually check for spark at the plugs. If the coil/ignition assembly sits right on top of plugs, a little more awkward but still possible to check for spark. If you have spark everywhere, use a gage and check fuel pressure. Are there any applicable trouble codes? When the problem occurs, Engine cranking, is there an rpm signal? Intermittent issues can be hard to track.

Yes, It could be an idle control issue. I wouldn't throw parts at it.

On older makes and models, I've seen where the mil wouldn't work for some reason, but, the scanner would show live engine data.

I've never heard of that? I have a low end scanner at home, will work on both obd1 and 2. I know in the cross-over years for obd1 and 2, some systems had hybrid datalink connectors. Don't know if yours is one? I'm talking a scanner that will show live engine data, not a code reader. If your datalink connector is 12 pin, common gm obd1 datalink connector. I don't know why you can't scan it? I double checked at MOD. Don't confuse code readers and scanners, two different animals.