tractor felt like one cylinder misfiring?

[oldboyscout]

I was running my Kubota 2620 today well after it was properly warmed up, then for about 30 seconds it felt like it was running on 2 cylinders. I could keep it running at high throttle but felt like it would stall. It was cold here but the fuel was treated. then it just ran fine again. wierd. Any ideas?

 

[Leejohn]

Shot of air or water. 1st guess would be air.

 

[oldboyscout]

I was thinking maybe it was a few drops of water in the fuel from the cold, but what do you mean air?