Agreed on sizing^. I'm also in Michigan and switched to Michelin Pilot Sport A/S 4's at the end of the summer. They are a bit louder than the Pirelli's but have treated me well so far and will likely run them all year since I'm not tracking the car. Good luck!
I agree, it sounds like it is coming from the rear, and I tend to notice it more when my fuel level is getting lower although there is still no predictability as to when it happens. I fear something is wrong with the pump or how it is accessing the fuel, but I do not know enough about mechanics...
@justinmiles -- how were you able to diagnose the fan as being bad? I have had my 24 GT PP for a couple of months now and I have been hearing a very similar noise that I have not been able to reliably replicate, and it is driving me nuts especially since I have less than 2k miles on a brand-new...