Weight Paint Help

Hi. First thing first, please check out this tutorial to understand why EA meshes are split and the purpose of cut numbers. Your blend has 3 meshes inside to interact with boots of different length. The bottom part of s4studio_mesh_2 overlaps with s4studio_mesh_1 and s4studio_mesh_3 and needs to be deleted. To do this:
1). Select s4studio_mesh_2, press TAB to switch to Edit mode;
2). Switch to vertex select;
3). Disable Limit selection to visible;
4). Holding Ctrl, lasso select first 6 loops of vertices;
5). Press Delete key and choose Faces;

As for your issue, if you click on any vertex of, what to call them, cuffs, you'll see that they have wrong vertex groups assigned.

To fix it:
1). Press B to activate box selection and select the same area i did;
2). separate it from the body by pressing P and choosing Selection;
3-4). Select s4studio_mesh_2.001 and delete all vertex groups in the special menu;
5). Click on the + sign next to rig to unfold it. Make bottom visible and selectable;
6). Select bottom, Shift-select s4studio_mesh_2.001. Switch to Weight Paint;
7-8). Choose Transfer Weights and By Name;

9). Choose Clean, scroll up a bit and choose All Groups;
10). Shift-click on s4studio_mesh_2, press Ctrl J to combine. If you switch shading to Solid, you'll see that the split areas are visible. They will be visible in the game, too. So switch to edit mode, press B, select these vertex loops and choose Tools - Remove doubles. Set merge distance to 0,0001