I would lube the cables and check the tension on them. Since it is a dual cable set up you may want to have them increase the tension on them. My throttle has a lot of play in the cables and I will readjust them once they break in and stretch a bit. However a faulty idle air control sensor can do the same thing.
The bike is over 2 years old, so shouldn't be any stretch problem. Also just had a full service too.
Interestingly, the workshop manager did mention the idle sensor on the phone.