Been there done that. First that was limp mode. All you need to do is pull over, turn off car, open door, close door, start car, and your good. This has happened to me a few times. Everytime was the same scenerio jumping off a light and bam its like hitting a wall. Best I can tell its something to do with either the engine boucning around in there and it either flips out the MAF sensor or the Knock sensor. I will say this has been eliminated since I have had a torque brace but Im not trying to say that was the problem but it has stopped it. Did you have hop when it happened. Im just trying to get data to show GM they have a problem.