i went with the pacesetter one, just because it was cheap, and my friend with a 4.0 has it and loves it. as for other mods, cool air intake, throttle body spacer, pacesetter tfx cat back. electric fan. after the header im gonna get a 4.0 throttle body, and be done with performance mods, b/c honesty there nothing left to improve without dumping loads of money into it.