Its an aero shield which also functions as an NVH absorbance panel to help smooth the flow of air under the car so it doesn't get dragged on the under carriage. Its actually quite sophisticated in design.
If you're willing to sacrifice the aero benefit as well as the fuel economy and protection of the engine compartment go right ahead.
Its a felt sound absorbance panel on top of a plastic or fiberglass core.
Moderator for: DURATEC Ti-VCT Performance, ST Performance, MK3 Focus