There is not a ton of things you can do to your 4.0 liter I6 engine to get more torque. The general consensus is to merely make sure you have the correct gearing for the size tires you have.

That being said there are some things you can do to get some mild gains. When adding them all you can see a noticeable change vs stock but may not be worth the money to do so. Here are the items that have shown performance increases, however small they have been proven on the dyno. I have not personally done any of these so I can only report what I have heard.

  1. Ported and polished head
  2. E-3 plugs
    1. Engine runs smoother as well as
    2. Increased throttle response
    3. Increase of torque
  3. Cold Air Kit and filter
  4. High performance exhaust header
  5. Performance exhaust
  6. Electric fan conversion
  7. Use Royal Purple fluids
  8. ECU tune

Avoid:

  1. Throttle body spacers

Unknown:

  1. Reroute crankcase breather to header collector, not the throttle body or manifold.