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Next question is what is you budget? Best bang for the buck is going to be rear gears and/or a CAI/tuner package with custom tunes. Either one will transform the car. Do both and you'll never want to get out of the car;-)
Two good upgrades for performance, but if money is limited I would do the CAI and tune first. As far as gears, depending upon how far you are going to go with performance it is often cheaper to simply upgrade to the 8.8" off a GT than to try to build up the 7.5".
Once you have the CAI and tune, the new gears, then look at new LCA's and aluminum driveshaft. That will help get the power to the rear wheels and to the ground.