sierra 01 performance bolt on's

Hi i am trying to figure out what are the best bolt on mods for a 01 4.8l v8 ext cab sierra, my father asked me to help him find some easy stuff that we can do our selves. what he is looking for is something that will sound nice and give him noticable power gains. he's not looking for all out power just some thing to maybe make it a little quicker.

so here's a list of what i was thinking

gibson cat back exhaust
gibson headers
volant cold air intake
new Ecu? (whats a decent one that is easily tuned)

thats all he's looking to do now and i realize that there wont be too much power gain but i thought i would throw the list out there to see if you think it will work well. Also with the gibson exhaust could someone point me in the direction of the exact model i need i went looking but was a little confused on which to get.

thanks for your time