Yes, at last. I knew whats wrong. First of all, my textures are very small. If you see the picture, all textures a tillable.

The problem is using the material option in the MED. Sometimes I just adjust the ambient/diffuse to darken/lighten the color because MED is like using some kind of color palate. What I mean is, if I use a .bmp texture, a 255,255,255 vs. 230,230,230 color produce the same output. Its like using a 8 bit .bmp (even I use 24 bit).

So, using ambient/diffuse on large object cause very low fps. Switch it off and just accept the final output.

I cant understand why MED or the engine automatically reduce the color palate. Even I use 24 bit .bmp as my flash screen (some logo), the color is reduced. Alternatively, I'm using .jpeg for my flash screen (which doesn't been reduced).