Your air control may be stuck and/or sticking. When the engine is judged "cold", the injector duration is increased causing more fuel to be introduced. This is done by the control unit. At the same time, the air valve/aux air valve/air control valve (whatever you choose to call it) allows more air in, increasing your idle speed. Your idle speed is not increasing. A cold fuel injected bike should idle @1500 rpm or so. As the engine warms, the injection rate is cut back and air valve closes resulting in less air and fuel. Consequently, the idle drops and smooths since the mixture is closer to what the ecm thinks it should be. Check and clean your air valve. I suspect you're fouling plugs because there isn't enough air introduced when it's cold.