[Burger Steak & Eggs]

No doubt this would provide the torque you are looking for, but installing and debugging it to run properly under all conditions would likely be challenging.

Have a look for some tweaks from a fellow called "Thundera" who had a 4Runner with a few bolt on mods. He discovered the 4.7 runs far too rich at heavy loads, and by installing an electronic sensor conditioning device, was able to recover substantial amounts of low end torque without prohibitive expense.