Will this diffuser scrape on driveways or steep inclines?

Rear diffusers sit low, so approach angle matters. Measure the ground clearance at your current bumper line and compare it to your driveway slope and any parking lot approaches you frequent. If you're already bottoming out, this addition will be noticeable. If you have typical street clearance, you'll be fine.

Is this functional downforce or purely cosmetic?

This diffuser is styled after the Boss design and follows that profile. Real aerodynamic benefit depends on speed, underbody sealing, and how it integrates with your full rear bumper assembly. Visually, it delivers the Boss aggressive stance. For measurable downforce claims, verify with dyno testing or CFD data specific to your complete bumper setup.

What should I do to prep the carbon fiber before installation?

Sand the mounting surface lightly to ensure a clean contact with your bumper. Carbon fiber can be finished as-is or sealed with a UV-protective clear coat to maintain the weave pattern and prevent yellowing over time. If you choose to paint or wrap, prep accordingly before adhesive or fastener application.