Its actually sounds like a very dirty throttle body, when the engine is cold and cooler, the idle air controller is allowing more air past the closed throttle body butterfly valve (throttle plate) so it runs good, but when fully warmed up the idle will suffer when this bypass valve is no longer bypassing extra air into the engine past the throttle body butterfly valve. Use a good safe cleaner and wipe the throttle body all inside as much as you can and open the throttle and clean as deep as you can and then while running a bit faster than idle spray cleaner into the other holes you may see where air will bypass the throttle plate. I believe this will cure your problem of stalling at idle.