(NO ENGINE LIGHT ON!) daring driving conditions at operating temp. this vehicle bogs down between 50-70mph in and out as if the cruise control is off and on. but it's off. when accelerating above 50mph it hesitates, then it bogs down before it picks up. only after i release my foot slightly off the pedal and then it kicks in again, and goes out again. when the weather was hotter, it didn't do it that much. now the weather is cooler, it does it quite often. 5-12 seconds apart some times. the vehicle drives great below 55mph and above 70mph. but it burning lots of fuel.

could this be an airflow problem? have cleaned throttle body, renewed air filter, fuel filter, a little change, but still blogs in and out.

thank you
Solo