[anthonyk]

Not terribly familiar with that bike, but I'd check for a disconnected vacuum line (if there are any), as well as cracks in the boots (if there are any) under the throttle bodies. Anywhere that air might get in.

That's assuming the easy stuff like sticky throttle cables and throttle tube have been checked.

Edit: If you take the airbox off and run it, you ought to be able to see if the throttle plates are stuck open. If so, it's probably cables or something else sticking. If they're closed and it's still idling like that, there's a vacuum leak somewhere.