Are you lacking power due to running larger than stock tires with stock gearing?
Your profile is not filled out, so who knows.
If so, a re-gear is your answer as previously suggested by UnlimitedLJ04.
Easy, cheap, bolt on performance upgrades do not exist for the modern 4.0 as also mentioned above.
How bout a cold air intake? Uhmmmm. NO. Waste of money also.