Will this diffuser scrape on steep inclines or driveways?

The rear diffuser extends below the bumper line, so ground clearance depends on your suspension setup and driveway angle. Measure the lowest point of your current rear bumper and compare it to your driveway pitch before installation. If you run lowered suspension, approach steep transitions carefully.

Does this add functional downforce or is it cosmetic only?

This is a stylistic piece that replicates the ZR2 design. Functional downforce requires specific ducting and airflow channels engineered for your vehicle's speed range. Use this diffuser for the aesthetic—any aerodynamic benefit will be minimal at street speeds.

What prep and finish should I use before installation?

Sand the surface with appropriate grit to promote adhesion, then clean thoroughly. Apply your chosen automotive primer and paint system. Allow full cure before exposing the diffuser to road debris or moisture. FRP responds well to standard automotive paint and clear coat.