Shiny texture

I used to be able to troubleshoot an issue like this, but its been quite a while since I repainted and I've forgotten a lot...
I'm trying to repaint the Searchlight Simulations 100 ton coal hopper into some generic NS schemes. When I place the default car in-game, the textures are applied dull and realistic. However, once I make any changes to the texture, it appears in-game all shiny and unrealistic. I know this issue is usually related to the Alpha channel, but for some reason I'm unable to update the alpha. I'm not sure how changing the texture would affect this in any way. Any help appreciated!
My repaint:
The original textures:
I'm trying to repaint the Searchlight Simulations 100 ton coal hopper into some generic NS schemes. When I place the default car in-game, the textures are applied dull and realistic. However, once I make any changes to the texture, it appears in-game all shiny and unrealistic. I know this issue is usually related to the Alpha channel, but for some reason I'm unable to update the alpha. I'm not sure how changing the texture would affect this in any way. Any help appreciated!
My repaint:
The original textures: