Silver plastic covers on engine there for a reason?

I removed the big silver plastic engine cover and the two plastic dinky silver covers for the spark plug coil unit top. Are these things there for a reason? Keep heat away? I took them out because I think they are cosmetic but let me know if you think I should put them back on???

Thanks.

Im not sure about the ones for the spark plug tops, I would assume them to be cosmetic..

But no they dont keep heat out, in fact they probably hold it in if anything. The only purpose I know of for the engine cover besides cosmetic reasons is that it does make the engine a little bit quieter because of the dampening material it has on the bottom of it.

Oh ok. Thats cool! I think Ill leave them off then. Anyone else know of anything then let me know. Thanks.