Sounds like it was actually a plugged accelerator pump jet instead of the main or pilot jets if rolling on slowly worked but suddenly opening the throttle caused hesitation. I had the same problem with my last bike, which was a 2000 Yamaha Virago 250. I let it sit for about 6 months, then got the bright idea to put a can of octane-booster in to clean everything out instead of dumping the tank and bowl and refilling from a can: REALLY BAD IDEA!!! A piece of varnish broke loose and plugged the accelerator pump jet while riding in rush hour traffic. No fun at all, and behaved exactly as you described.