The problem with Toyota engines that hesitate is usually a combination of bad fuel, low octane or water condensation in gas tank and or Air flow issues in intake pathways. Take the air filter housing loose and open up the intake air path to the air intake butterfly, accelerator. Get some carb cleaning spray and clean out the intake with a rag and spray. Next have someone test the mass airflow sensors for you (Oreillys or Autozone). Often the mass air flow may be covered with soot as well from carbon blowback in intake area of engine. Use premium gas every now and then and put a can of B12 Berrymans in fuel tank and oh yeah, change the sprark plugs every 100000 miles.