I had a similar situation with my daughter'* '91 GP. The first time, replacing the crank sensor took care of the problem. It'* low on the backside of the engine and is a stretch to reach. The plastic cracks and warps which makes it intermittent. That took care of the problem until 3 months later when the ICM went...same symptoms.
The crank sensor was only about $30, and is held in with one bolt. Reaching it is the hardest part. The only accurate way to test the ICM is by replacement. You should be able to pick up a used one at a junkyard. If you're getting no spark when it dies, it'* likely one of these parts.
Black 2000 SSEi, Silverstar Headlights, Angel Eyes fogs, 3rd brake light overlay, hi-flo cat, drilled 180 degree thermostat, Intense FWI, PCM, shift kit, and 3.4 Pulley. Solid front mount.