'94 Buick Regal - Intermittent cut out while driving

Folks,
My 1994 Buick Regal has developed a problem that is driving me crazy!
First, details on car: 133K miles, 3800 V-6 (Code "L"), 4T65E
transaxle, California emissions (has dual O2 sensors). Has that weird 1994/95 ECM system that is OBD1 electrical interface (12-pin ALDL connector) but puts out OBDII DTCs. Recent maintenance includes new battery and smog test for license plate renewal (no stored DTC codes in ECM per the smog tech).
What is happening is that the engine will just quit while running. Happens when throttle not depressed (decelleration) with or without brake pedal pressed, during both straight ahead running and turns. Never has happened when car is standing still at idle. When this happens the Check Engine light comes on (but not before stall, just afterwards) AND the Air Bag light also comes on and flashes (does the same power-on self test routine as when the car is first turned on).
Whole routine is highly intermittent - car can go for 3 weeks or more between episodes or do it 6 times in one trip home from the office (as happened yesterday). Also, engine does not hesitate or buck before shutoff (the action one would expect if it where a fuel starvation problem) - acts just like you turned off the ignition switch. All other electrical devices such as the radio and HVAC blower do not quit working at any time. Once you put the car in neutral the engine will restart immediately without hesitation.
I'm thinking intermittent loss of electrical power to the Ignition Module and ECM - traced schematic and the ignition module, ECM and SIR controller are fed from same path through ignition switch (fuses for ignition and ECM fed from common line from ign. switch to Underhood Center #1 and air bag feed from same contact on ign. switch via feed to fuse box in glove box). Checked the fuses, connectors etc. on this path but could find no obvious problems. I've also checked the ECM & ignition grounds under the ignition module bracket - they are solid (I've had problems with those on my old Olds 98). I've discounted (for now) crank sensor, ignition module and such because of air bag light coming on.
Any tips from the group would be appreciated. I'm real leary of taking the Regal to the dealer's service dept. - I've worked on cars and electronics long enough (40+ years) to understand that troubleshooting intermittent electrical problems can be a real bitch and also that too many mechanics will just shotgun it (throw parts at the problem) until the problem goes away. Cannot afford to do that.
Ian, I would especially value your evaluation of the problem. From your postings you seem to have an excellent grasp on some of the weirder problems that afflict GM cars.
Thanks in advance for any help the newgroups can provide.
Regards, Bill Bowen Sacramento, CA
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Very true, Bill. I had an 89 Regal that did just the same, and multiple trips to the dealership availed nothing ("We cant fix it if it isnt acting up"). Warranty is worth nothing if they cant fix it, right?
I have know some people to trade their cars they got so frustrated with this sort of problem.
Ian is an excellent source of reliable information.
In my case, the Buick zone representative recognized my problem as being an ECM which was constructed during a run using bad semiconductors. He ordered it replaced with no further haggling, and the problem was solved. Yours is probably something different, but I can appreciate your quandary
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