Ahh, fun anecdotal 'snow' visual observations...many have chimed in on that ,especially in the snow zones. The snow flurry/water droplets/dust vortices does give good sense of flow movements. Taped-on yarn tufts are always good to study general/specific areas of your vehicle aerodynamics (with requisite CCD cameras at critical areas). But it is the proven modding that gives real results. Example of a three-box (sedan), thanks from a fellow eco-modder study.
Most have done it for extreme aero/best fuel economy, very different criteria from your racing modes. Some important downforce may be required for safe handling performance at top speeds. A scenario of a wide hi-speed decreasing-radius turn, you may need some rear downforce (some trim tab) to tidy up your rear. Neon's fwd, inherently an under-steering dog. Your suspension setup needs to be tweaked in a low-drag profile.
Most will recommend a fastback modification (top-speed numbers), the 'most bang for the penny' budget that you have. Study the templates and many comments from eco-modding practitioners with their own real-life 'test' vehicles.
Very interested what you will implement and eager to follow your tests/races/performances. Good luck.