If you want better torque you want a beefier rear spring if they make that for your setup. Smaller front chain sprocket and larger rear sprocket will torque it up even more. It made a big difference on the mini bike mule project and got full pulling power out of that 6hp engine.
If you can get a better belt do it. Your best bet is to take your existing belt out while it is still in one peice so you can measure it and cross reference it. Might still have some belt numbers printed on it.
Pay close attention to how the sides of the belt are shaped. Generally two types symmetrical (V shaped) and asymmetrical (one sided angled the other side flat) check the angles and most importantly the width. If it's too wide when the ATV is in idle neutral it will still want to drive as it catches the lower portion of the pulley. You can measure the angle needed from your pulleys.
I do think you want to avoid using belt dressing on these as it may mess up how the belt rides up and down the pulleys.
That's all I know about the subject.
