Probably the spark plug, but repeat change the filter. Based on past experience with brand X, water in gas will "globulise" at the filter and cause intermittent problems long after the actual contamination. Sometimes gas line antifreeze will clear it, sometimes not.

 

I changed the filter, pressure line to the quick disconnect and the plug wires yesterday and rode about 60 miles with no problem so I am keeping my fingers crossed that it fixed the problem.