I'll get my shot in before the experts arrive.

With 3.21s, your plan should be weight. You'll suffer from piggy gears if you add too much weight to this Jeep. The first of these mods your talking about should be the intake. AFE's is good. you'll get better sound and throttle response.

People who say they do nothing are wrong. For the 300 bucks, your Jeep will sound better, and feel better. The exhaust I care for less. If you only buy one, do the intake.