Car starts, but starts to jerk and shuts off in drive or park

LT model. Car starts, but within thirty seconds it jerks and shuts off. The car almost wants to shut off turning around corners and when gas pedal is pressed it is almost to floor to keep running. There happens to be some what of a jerk after car is accelerating whether it's at 25 mph or 60 mph. Replaced exhaust manifold, still stalling. Replaced spark plugs, and car seemed to run normal. Took for a test drive stops and goes. Got up to 50 mph some hesitation. After the drive I sat in the driveway in drive and car shut off again a couple minutes later. As well as in park. Before the test I let the car run for 25 minutes or so, and there was not any sign of it stalling at that point. No check engine light. No codes. Please help!