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RocketSled and novetteyet are both on the right track.
With a weight/power ratio of about 6 lbs/bhp, and a basic design that puts the Cd in the .29 - .35 range to begin with, there isn't a lot of payoff for the time and money invested in trying to reduce a Cd of .34. Wind tunnel testing is very expensive, and time consuming.
Reducing Cd will get you more top end, and better acceleration above about 120 mph - but for practical purposes, that's about it. Since the vehicle has to have certain protuberances for brake cooling and heat extraction (and those are themselves are constrained to a certain extent by aesthetics), you could spend tremendous time refining the size, shape and position of those elements and see almost negligible decreases in Cd.
Cd for a car like this is driven by: (1) the rate at which the maximun cross-sectional area (viewed head on) tapers to the rear - i.e., how gently the pressure can recover (strike one); (2) the frontal area of the front grill (strike two); and (3) down force (strike three).
Given the basic size and shape the car had to be, the Cd is not bad, IMHO. More to the point, I'm sure the car's Cd is already the product of a lot of design trade offs, as well as griping, whining, and pleading from the aero engineers.
(I used to design military airplanes.)
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