studdering on accel. only after heating up

My S10 Overheated on the mountain road. the check engine light came on so I pulled over for 30 min. till cooled down. Started back up, light off, but studdered when accelerating. 6 months ago, now getting around to fix it. Starts fine, runs fine (no studders) until it drives for about 5 miles then starts studdering on acceleration mainly in 3rd and 4th gears, not notice any studdering in 1st, and no studdering when maintaing constant speed. Changed: water pump (still overheating), thermostat (still overheating), fuel filter (still studders), O2 Sensor (still studders). I have a feeling this is probably a simple problem (one of the other many sensors), but which one do I check next: Coolent Temp? Throttle Position? MAP?

Welcome to AF. First of all what year what engine, you must post all the info here, also mileage!! Have possible head gasket issues been checked, any cel or pending codes? You are just replacing parts, where are the diagnostic basics?