jwjones,
I'm sorry to hear of the troubles with your G6. Your issues may be caused by the hub assembly, tie rods or sway bar. It can be difficult to diagnose over the internet. I encourage you to take the vehicle in for an inspection. A certified technician should be able to offer a more accurate diagnosis after a physical inspection.
Please keep us posted.
If you have additional questions, please feel free to contact me.
Louis
GM Customer Service