I hate to bring up this old thread, but it sounds like I am having the same problem as the OP with my 2011 SEL. Driving along, let off the gas when someone ahead of me brakes, then when I go to accelerate again there's a bang and the whole car jerks.
I see there's a TSB out for this, but I was wondering how much this problem might cost to fix, since I'm outside of my warranty?