Will this diffuser hang low and scrape on steep driveway angles?

The GT Concept profile extends lower than OEM designs for visual impact. Before installation, confirm ground clearance on your driveway slope and any frequent ramps. If clearance is marginal, plan your approach angles or consider a lower lip protection strip to prevent contact during steep entry.

Does this rear diffuser actually improve airflow, or is it cosmetic?

The GT Concept geometry is designed to channel rear airflow and reduce turbulence behind the vehicle. Real-world effect depends on driving speed, vehicle setup, and overall aerodynamic balance. It functions best as part of a complete aero package rather than as an isolated component.

What finish should I apply, and do I need to seal the carbon fiber?

Real carbon fiber is porous and will discolor without protection. Sand and prep the surface before applying your chosen clear coat or UV-protective finish. A high-quality clear coat protects the weave from oxidation, UV damage, and weathering while preserving the visual texture of the twill pattern.