well there isnt really parts u can bolt on for torque except for a SC. But u can free up some low end. Light weight rims, change the break disc to some drilled slotted disc that weigh less, the small UD pulleys, lightweight flywheel. Basically lower you rotational mass. The less weight u have to get moving, less time it takes to get it moving.... and everyone complained in highschool psyhics class we would never use that useless knowledge again
A torque converter is the mechanical equivalent of a clutch for an automatic transmission - it's the thing that keeps your car from stalling when you're stopped at a light, among other things. If your GT has a stick, you don't have / don't need a torque converter. If you have an automatic tranny, you can swap out the stock torque converter for one is optimized for your Tib's RPM range. I don't know if the stock automatic Tiburon has a locking torque converter - if not, replacing the stock one with a locking TC will ensure that 100% of the engine power makes it to the wheels once the converter is locked.
The clutch analogy is a good one - with a stick, you get to decide (with your left foot) how much of the power from the engine gets to the wheels. A torque converter makes that decision for you, so replacing the stock one may help you get more low-end torque to the pavement.