2006 vfr idle and throttle issue help

I was looking to buy a 2006 vfr 800 with 30,000 kms. All stock except slipons. According to the owner it has been sitting with very little use for 1-1 1/2 yrs. The fuel was almost that old. On start uop it idled a little rough but under very mild throttle it acted like it was missing. Medium throttle it seemed better but not there. We added some fresh gas to it and I test rode it. Under light throttle it was very rough almost surging. Rpms also seemd like they came up real quick. In 5 and 6 gear at about 60 kph the bike had a real pronounce d vibration only under mild accelleration or heavy accelleration. Took it back and hard reved it a few times in the garage and got some heavy blue smok out of it. Took it for anoth ride and rode real hard and it seemd to be better but still not there. Do you guys think its just something that will clear up with a good dose of seafoam and a good highway haul or maybe walk away.