Can I use specular map in game mode? I turn off diffuse on material and turn on specular map. In game mode I can only see diffuse map on object…
you turn of diffuse but you still see diffuse? 
yes you can use a specular map, you turn of specular (not diffuse) then head to texture add your spec. map, scroll down to the influence section, here you see 3 settings under the head specular, play with it to get the options/look you need.