I've made a custom folder and saved the textures for a set I have in there with the right names such as r_pecs.tga and l_leg.tga, but for some reason the textures don't want to show on Tori? The only texture that shows is the head.

Give me a screen of your folder and of the tori when you load it please. :>

Folder
Tori

Did you edit item.dat to have 0s instead of 1s where necessary? e.g.

TEXBODY 0; 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
TEXJOINT 0; 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

TEXBODY 0; 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
TEXJOINT 0; 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Do I need to change the bolded 0 to a 1?

No, you must change all the 1s there to 0s.

Just try it rn, to turn the bolded one to 1, i meam

Changed all 1's to 0's and it did nothing.

did you change these 0's to 1's
TEXBODY 0;
TEXJOINT 0;
if so revert those ones (and only those ones) back to 0

Nope, I kept them the same.