95 ranger 2.3. It has 327,000 miles on it so I know it has some wear, but in hot weather it hesitates something awful. When you take off it will choke down and several seconds later start to pick up speed more like it should. It is sick in hot weather and always has been. I have replaced the coolant temp sensor and air filter and MAF sensor and IAT sensor and DPFE sensor none have helped. Once in a great while it will sound like a small backfire through the intake when you stomp the gas or downgear real hard. When the weather cools off, it runs fine again. At night I can climb a hill in 5th gear better than in 4th in the hot sun. What could cause this?