Couple of things. If it surges with no throttle then it is most likely an air leak. I have found the ignition side crank seal to cause this same problem in the past. If your seals are 5 years old, you should replace them.
If it revs like that when you apply throttle, but does not come back down, then be aware that there was a recall on the plastic wheel in the throttle assembly (at least for the '01 model). The cable gets caught between the plastic wheel and the throttle housing and results in a very dangerous stuck throttle condition. I got the recall notice, went to the dealer to get the replacement wheel and he told me that I had to bring the whole bike and have him replace it!! I wound up getting a Motion Pro unit instead.
Whatever the cause, DO NOT ride this bike without fixing this condition.
Hope this helps.