Mine seemed to start doing it more now when it's wet. After a car wash or when it's raining. I bought some "Jig a Loo" spray lube...it's a silicon type and it has helped. Good Stuff.
I sprayed it where the column comes in the inside part of the firewall. There is a dense, grey sponge type material around the boot there (like the stuff they pack electronics in) that was even squeaky when you ran your finger over it.(like fingernails on a chalk board) And it has worked so far. Clean, not greasy.
The dealer said there really isn't much you can do do about it. Just had it in for brakes and crankshaft seal and they said there is really no places to grease it under there. I thought at first it was inside the steering wheel itself, but narrowed it down to there. They do a pretty good job checking everything out.
Shame, GM is doing away with Pontiac. I really do like my G6.