04 silverado z71 4x4

i would say almost everyone has a vision for their truck as soon as they get it. the minute i drove away from the dealership with my truck i knew what i wanted to do. iv already had flowmaster exaust installed and i plan on getting cold air intake in the near future. but i was wondering what else i could do thats relitively cheap that would give me a noticable gain. and while im already here i was wonding if their is any way to lightin up the 4x4 tranny? because its just to heavy to race with and i dont think a stock tranny is going to be able to handle the power i want to push in the future, as well as the weight it adds, but the thing is i really need a 4x4. i know im kinding looking for a weird combination considering the power i want to push in an off road truck but i think if done right it can be sick. help please =[