Will this diffuser scrape on driveways or steep inclines?

Rear diffusers sit low and follow your OEM bumper line, so clearance depends on your current ride height and suspension setup. Verify your ground clearance before installation, and test your typical entry angles after fitment. Lowered vehicles need extra caution on steep inclines.

Is this diffuser functional for aerodynamics or purely cosmetic?

VRS-style diffusers are designed with functional channeling to help manage rear airflow and reduce lift at speed. You'll see real aerodynamic benefits on the track; street benefits are more subtle but present. Visual impact is immediate either way.

What prep and finish should I apply before installation?

Sand the carbon fiber lightly to remove any surface dust, then apply your choice of clear coat to protect the weave and seal against UV. A quality automotive clear coat will preserve the finish and prevent oxidation over time. Install after the finish has fully cured per your paint product's specs.