Will this diffuser scrape on driveway ramps or inclines?

Circuit diffusers mount using factory fastener points and maintain OEM ride height, so clearance matches your stock setup. If your vehicle currently scrapes, this diffuser will have the same behavior. If stock clearance is fine, you're good to go.

Does this provide real downforce or is it cosmetic?

The Circuit profile is designed with functional blade angles that generate downforce at highway speeds while delivering aggressive aesthetics. You get both — it's not a cosmetic-only piece.

What finish prep should I do before installation?

The diffuser ships with UV-protective clear coat applied. Before mounting, clean the mounting surface on your vehicle with soap and water, then dry completely. If you're repainting or refinishing the diffuser itself, sand and prep the surface before applying your chosen finish.