1991 Ford Tempo car runs rough after warming up

Recently towed a small trailer, started to run real rough, missing and sputtering, could romp on the throttle and it would run but then at idle again would spit and sputter again. Replaced O2 sensor, plugs, wires, cap rotor. Found a small pin hole in the heater bi-pass hose, fixed that and discovered the anti freeze was spraying on the two sensors in the thermostat houseing. So dug into that and replaced thermostat and the bi-pass hose. Car will start and run like a dream. Almost down to the tick, as soon as the car hits operating temp, it will miss and start to spit and sputter and like it won't even get out of its own way.