does your car get heavier with body kits or lighter? it think adding body kit will drop weight..coz front bumper and rear bumper replace with carbon fibre kit..am i making any sense?

I can't imagine you would gain any weight. You're not going to loose a whole bunch of weight either. Its basically the same amount of material either way, but CF would most likely be the lightest out of stock plastic, fiberglas or CF. Its not a performance upgrade in anyway.