Will this diffuser scrape on ramps or steep driveways?

The SP-N profile sits lower than OEM for that aggressive look. Check your driveway angle and ground clearance before installing—if you bottom out regularly now, this will too. Approach steep inclines at an angle to minimize contact, just like you would with any lowered setup.

Is this functional downforce or purely cosmetic?

The SP-N profile is designed for visual impact first. The undertray channels do create minor aerodynamic flow, but don't expect measurable downforce gains at street speeds. Install it because you like the look—any aero benefit is a bonus.

Does carbon fiber need any special prep or finish work?

It arrives brand new and ready to install. A protective clear coat is recommended to keep the twill weave looking sharp and guard against UV fading over time. Sand and prep the surface before applying your chosen finish if you plan to paint or coat it.