Under acceleration or a constant speed? If under acceleration, could just be the tires fighting for grip in the cold temps. 40F is very cold for a summer tire. Any noticeable difference with various road surfaces, such as grooved roads causing some tramlining? New tires tend to tramline more as the tread grooves have sharper edges and can catch on surface irregularities and grooves in the road. Even when I replaced all 4 PS2s with Michelin Pilot Super Sports I noticed no such squirming under any condition, but I replaced my tires dead in the middle of summer. That was on my previous 997S. I'm about to replace all 4 PS2s on my current 997S with the Super Sports again. It's warm out already and will be interesting if I detect any squirming when new. I don't expect to although I will break them in for a few hundred miles.

 

I think cold tires and incorrect tire pressures may be more to blame. I recently purchased a 2006 C4S and the car seemed to dart all over the place at hwy speeds, After chkng tire pressures they were way too high and uneven ,....so reducing and balancing them better the problem was dramatically improved. Good luck