I have a 03 Honda VFR 800 VTEC and A similar problem to yours. If I go out on it and travel 60 miles on it approx it will stall at least once when changing down the gears. I have gone back to the main dealer who has phoned Honda and had a reply that one other 800 vtec has had this problem and this was down to the ECU. The bike is going in on Thurs 11th Aug 2004 to have this changed.