Engine spits sputters and cuts off

This sounds like you have low fuel pressure. Here is a guide to help you check the pressure to confirm a weak fuel pump:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Fuel pressure (Key "on", Engine "off") 384-425 kPa (55-61 psi).

We should run the codes as well.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Please run down these guides and diagrams and report back.

If it is the pump here is what you are in for when replacing it, you can get an AC Delco pump on Amazon for $216.00.

https://www.amazon.com/gp/product/B001FKZ4L4/ref=as_li_qf_asin_il_tl?ie=UTF8&tag=2carprcom-20&creative=9325&linkCode=as2&creativeASIN=B001FKZ4L4&linkId=8ecbee70a87fa845ecea100f2939bf7d

https://www.2carpros.com/articles/how-to-replace-an-electric-fuel-pump

Here is what it will be like for your car.

Cheers, Ken

I would install the spark plugs it calls for and also have you replaced the crankshaft angle sensor? When this sensor goes out it will not trigger a check engine light.

https://www.2carpros.com/articles/crankshaft-angle-sensor-replacement

and

https://www.2carpros.com/articles/how-to-change-spark-plugs
Spark Plug Type GM P/N 12568387

Check out the diagrams (below). Please let us know what happens.

Cheers, Ken