It adds 0.0000000000000000001482761 lbs and thereby makes the car slower. No.
Personally don't spend any resources prettying-up things that remain out-of-sight, but
@Crv 's engine cover does look pretty good. Mine of course would be Kona Blue. π
Engine cover removed, our engine isn't exactly pretty... lots of "random" lines running in every which direction. (photo from different model vehicle)
If you do it, be sure to follow up with a photo or few. Curious.
For the uninitiated, the plastic dome piece is some part of the exhaust manifold I believe. Shows how far plastics have come.