It was 95 degrees outside, engine temp was steady at 195 degrees at 65 mph. Engine begins to stutter 1 hour into my cruise. I pull over to the side. Engine still idles but will not throttle up. Turn off the engine for a half hour and the car starts and run fine the rest of the day. This happened twice this summer. I did not have my scanner with me at the time so I have no numbers. Stock MAFsystem. What might it be?