IM ready to give up

Do you have a check engine light?

https://www.2carpros.com/articles/engine-hesitates

Could be caused by one of the following below

Oxygen sensor.
Catalytic converter.
Fuel injectors dirty/sticking.
Mass airflow sensor/Airflow meter.
Throttle position sensor.
Crankshaft position sensor
Knock sensor
Manifold absolute pressure sensor.
EGR Valve
Fuel pressure regulator leaking or defective fuel pump.
Fuel contamination.
Foul/defective spark plugs.
Open spark plug wires.
Ignition coil/Coil packs defective.
Incorrect ignition timing.
Cap and rotor.

Note:If it doesn't apply disregard it and keep testing.

The egr valve is on the intake. Remove the valve and clean the hole out. You may have to replace it.

Remove the oxygen sensor from the header pipe, roadtest it and see if the problem is still present. It sounds like the converter is plugged. As the vehicle sits, the debris falls down to the bottom of the cat, as pressure flows through it, it picks up and starts clogging. You create an airleak by removing the sensor, allowing for adequate airflow for the engine to run properly.

Youll also need to know the fuel pump pressure when you are having the problem. Gm pumps overheat and just quit. Later you come back it will start again for 20 min. Good answer to gstacey thanks for using 2carpros

Hook up a gauge so you can see it. Like through the cowl area. Watch the gauge as you drive. When the probem happens we need to know the fuel pump pressure