That big rear face is an aerodynamic disaster, imho. Which is one reason why the EPA numbers for that car aren't so good.

Anyway, the idea to clean the MAF sensor and change the O2 sounds good to me. Relatively low cost. And the wheel spinning thing too. I should do that test on my car.

I've got an idea that fitting a trunk box on that shape would improve rear aero. Flat surface immediately below rear screen, 1ft wide, tapered sides, paint a whitewall tyre on the back for period charm....

The drag coefficient is .39. Not much you can do about that.