Bought 2009 Tahoe that was "new old stock" from Chevy Dealer in December 2015. It had never been titled. It had been used for a CS vehicle to promote Hybrid for GM until it reached 2800 miles. Then parked on their lot. Purchased for a good price and less than they were asking for it. They just wanted it gone. Has just about 8000 miles now. Has always had a vibration. Seems to be in the floor not steering wheel. Been to Discount Tire several times to rotate and re-balance tires. Tire folks do not think its the tires they are sick of seeing me. Before I take to GM has anyone ever had a similar vibration issue?