[flyin low]

Maybe a bad o2 sensor. I would put a few hundred miles on it and see if it goes away...

 

[flyin low]

I suppose there is always a chance but if it was doing this with the previous owner then some damage could have all ready be done... but it really sounds like an o2 sensor as that is what controls your air/fuel mixture... I would still put some miles on it as it could also be the gas that is in it or some sort of fuel additive so at the very least I would run the fuel in it out pluse one more tank full or drain whats in the tank and run a tank of "new fuel" through it witch is still going to be a few hundred miles or about a days worth of riding...