why does it Lose power/stall when warmed up, approx 15 miles of driving?

What is your question?

If I am on flat ground at 12-15 miles (65 mph), hiccups with loss of power. If trying to climb hill at 12-15 miles (35-40mph), loses power and stalls but starts right back up. Fuel pump and filter are good. Throttle body sensor has been changed. Open to suggestions...PLEASE