2003 f150 runs like it has water in the gas

I drive about 1,500 miles a week. Heading into southern Texas, my truck acted like it was starved for gas, never died, but ran rough. Had fuel filter, and fuel pump changed..drove 15,000 miles without a problem, did it again for about 200 miles, stopped for the night, it continued the next morning, drove 100 miles. Then it stopped..Drove about 12,000 more miles, then it did for 150 miles, then stopped
I have changed filters, tune up, oil change, different gas,,the only thing in common I see is when the temperature outside gets over 100 degrees, has all ways happened in the south..any ideas?