I just replaced these gaskets on my '07. Not cold enough yet to see a change, but by looking at the difference between the old and new rings, I am sure this will be it.
By the way, this job was a major PITA. It's certainly doable (with a lot of patience), but the gasket on the driver's side closest to the firewall is near impossible to reach. Once all the gaskets are out, it's a cakewalk, but until then, have something to punch in your garage.