When I Start My 2000 TW with the choke on, it will rev really high until I partially turn down the choke to half or off. Then idle is normal. I dont choke my TW very long(30sec or so). Hope this helps.
Very good possibility because The previous owner to my bike put a new carb on the bike. Looks factory, but that doesnt always mean anything. Normal operation it works perfect, but very high throttle with chock on.