I agree it shouldn't make much of a difference. I actually asked someone from Jogon Automotive who already made the carbon engine cover for the i4, they say it weighs around 1.78KG with two layers dry carbon fiber fabric and 2~3 clearcoats. I don't know how's that compared to the original...
Jogon automotive already made a full carbon fiber engine cover for the i4, I've asked some pics from one of their sales Lynne, as many of us are waiting to see how they will make it for the v6.. looked pretty sick compared to the original cover on the i4