Nothing I've found, BUT you can shave them, then any 17 except OZ will fit. It's very very close, but most will fit just fine. I want 17s because I want drag radials...is that too much to ask
There is something about the wing, I really don't have a clear answer for you, whether variances in road conditions, weather, or I just drove slower (not likely) I really got better fuel mileage with it on.
Two things you should do as soon as you have the chance. One is to remove the muffler, it's not quite 50 lbs of dead weight and there is just a little bit more open tone to the exhaust, the turbo does good to keep it quiet anyways. Two, buy some of that corrugated plastic sheet, Cover up everything under the trunk out to the bottom lip of the ground effects use large head rivets or something equally strong enough to handle constant wind road elements and rain. I also did the front but may have lost a bit of intercooler efficiency. It's actually rated higher in capacity than what it comes with from the factory. Next, and probably the only true benefit without any real work involved, a tune.
Ohh and you wanna see awesome, pump your tires up to 40 front/38 rear. The factory conti sport2s are ok, but they take overpressure pretty well. Anyways, I haven't got terribly evasive yet, If you walk by the car, it looks like a Cobalt...pretty much stock, go underneath it and it's obvious I've been making an effort to keep it somewhat aerodynamic.