That said, they tried to pull the same thing on me. I took mine to a tire store that I purchased tires from before and they balanced them for free! Then I took it back to the dealer saying that tires have been re-balanced. Dealer then proceeded to continue diagnosing... GM field engineer, PICO scope, two new tires, no improvement. Second dealer, two more brand new tires, GM regional rep, GM field engineer and two Goodyear engineers from Ohio. Match mounted and all tires balanced within 5lbs or less. Decent improvement. Not the best outcome, but wasting anymore time of my life I knew it was going to get ugly past this point.