For the exhaust, go with GMPP and the intake manifold I would as well. At least if I were you.
Some things you don't have to, like struts and stuff (I went with coilovers by B&G), but I did buy my lower control arms from there. Also if you are talking CAI, get a K&N, Injen, etc. They IMO look better than the GMPP.
GMPP does have a lot of mods that are proven and reliable which is nice, so you can't go wrong with them in most cases.
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