Hi all. This is my first post on this forum and I hope you can help. Bought an '07 Grand Prix for my son for school and have noticed a bucking/surging with RPM oscillating around a few hundred revs when under light throttle on a slight upgrade. At first I thought it may be shudder from Torque Converter but can also happen when selector is in 3rd gear. Accelerating seems to cure it. Any thoughts will be appreciated. Thanks