As far as headers, I don't think anyone has done a real head to head. From what I have read, shortys are pretty much for sound in this car. Long tube headers will get you more respectable power, provided you are up for getting a tune. Trifecta seems to be the only available tuner and there still seems to be an experimental quality to what they are doing with aftermarket stuff. As far as exhaust goes, none of the Cat-backs have shown more power. I think the stock system flows pretty well except maybe the mufflers. Bottom line, you are not going to get more than 10-15 HP with the available options. Plus that 10-15 HP will cost you a few thousand dollars. Browse around in the V6 forum a little, you will see what I mean.