I would suspect a sticking ICV as the drop in RPM"S indicate a form of working condition. The best clean is remove the two pipes give the ICV a thorough cleaning with carb cleaner ,next should be a cleaning of the air intake bore ,if you keep the throttle in full open position you will be able to clean right to the end of the butterfly area. check for operation of the idle switch connector,clean.Hopefully this will get you started on the right track.
mak
pk.