it's called gouraud shading and is best to turn off with pappenheimer's tweaking or open the model in MED, go to its skin, go to its material settings and put all the diffuse on zero and turn up the ambient.

however, it shouldn't be necessary to change such a simple geometric structure to a model to increase performance. i'm no expert but using the WED block version (with [detail] flag set) may help your fps and still have the precalculated lighting.

galen's flat-shading may suffice depending on what you're going for.

julz