Hay man, I had a similar problem with my Runner.
It turned out to be the fuel pump. The fuel pump can cause some odd things to happen. Mine seemed to be affected to the amount of throttle applied. But just like yours if I turned i off it would be okay. I first replaced the fuel filter, seemed to help a little (secondary problem).
Start with your fuel filter as it is easier to replace and should be changed with that kind of mileage. But make sure your wires are in good shape and the cap is not corroded badly. Other than that consider the ignitor as a possiblity.