You need to use custom lighting for that, also, don't forget to Constant Clamp the Lambert term ;P I remember asking the same question, and Jordan (one of them Epic artist peeps) told me in the thread that using Diffuse directly is showing off all the information, even those you don't need since it's already the diffuse…
Thank you very much! Working fine. Now i added "custom diffusemap" (temporarily its just a color) with shading and working nicely too. I cant wait to try this in a complete scene :)