Brought my 2007 G6 GTP (3.6L) in for service Monday .Was driving down the highway, the Traction OFF light came on, and the car started misfiring, surging, bucking, stumbling...you name it, it did it! Was able to make it a few miles to work. Then I restarted the car....seemed to run ok as long as I applied at least light throttle....on coast, the car bucked..(it has always done that, but now much worse) Report back from the dealer is that it threw a code P0021, which says the cam position sensor was giving faulty readings. They did a partial teardown on one side, and found the camshaft had excessive lateral play, which at the extremes of play would cause the camshaft sensor to not read. The play had also caused significant wear on the cylinder head, so both cylinder head and camshaft need to be replaced. Unfortunately, they are having trouble locating parts. This is the third one they have seen with this issue, and GM is certainly aware of it. Dont know why i keep buying Pontiac....each and everyone has been a nightmare! Car has less than 11,000mi.