I noticed this problem when I first drove my 2009 LTZ (6 speed) but it seems to be getting worse. If I'm cruising down the highway at 65 and take my foot off the accelerator (such as when coasting downhill) the transmission *really* pulls on the engine and then I get a "shudder" as if I tapped the brakes slightly -- enough to make my head move forward/back. I've been experimenting with this and it's driving me crazy. With my Grand Prix, when I would take my foot off the gas, it coasted like a son of a gun; my Boo doesn't seem to want to coast at all -- when I take my foot off the gas it feels like I hit a gust of wind coming at me -- the slow down is very noticeable. Has anyone else experienced this? It seems to be at its worst in 6th gear, but I notice it in 5th as well (I would expect this if I had manually in 5th gear and revved up and I took my foot off the gas, but not at 30mph on the level).