Many will like it off but I personally like the plastics on.

 

I think the plastics are there to keep the high pressure air from going around the intercooler to the back side of it. If the pressure is high in front, and lower in the rear, air will be sucked through the intercooler; Not just rammed into it.

I also think it serves the purpose of making the intercooler look symmetrically mounted. Its quirky end-tanks make it look like a custom aftermarket afterthought.

 

plastic covers look better, IMO. Im not a fan of seeing charge pipes, just intercooler cores.