[eippermx]

Makes me wonder if you have a bad crank position sensor CKPS). Use the search function in this forum and read up on it. Like the MAF & MAP sensors, it can become flaky causing intermittent stalls and not turn on your SES light. RichTazz and Bob N. have written a bit about the CKPS in this forum.
Question:

Have you taken the car to a GM dealer and have their mechanics hook up their diagnostic equipment to your PCM? The dealer can see frame by how your car is running...