I think the problem is related with the second uv map. The "Uv_1" since your mesh doesn't have one it looks bad in the game. There's some tutorials about it in the forum. I don't have much experience myself in this type of cc, but I'm sure someone will pass by and help you! good luck
Please do not PM me to help you with your creating problems. You can post in the Creators Help so everyone can see the problem and solution.
There's quite a few issues with your top. For starters it seems to have an extra texture file that isn't a specular/bump/diffuse, I've no idea what it's meant to be.
Lastly, your top is 15k vert/29k poly. That's an astronomical number considering minus the folds around the tummy your mesh is essentially just the nude torso (meaning it's flat). You have the full body meshed, and the top meshed over it. You don't need to have the body meshed under the shirt since the shirt IS your body mesh. And your shirt consists of far too much geometry. You can either remove the body parts under your top and decimate your top to slash the poly count, or you could redo your top entirely by cloning off of that one basegame top that's very similar to your mesh:
Ideally I'd say anything over 3-4k poly for a t-shirt is too much, unless it has a lot of detail.
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