I would also go with the reply that it is either 'Throttle Position Sensor oe mass air flow only two things that would most likely cause this problemo. Good Luck in the world of Diagnostics. A Bi Directional scanner is a good purchase!I would check the ECU error codes. You'll need an ECU code reader to plug in and access any stored errors. The error number(s) will give you an indication of what's causing the problem.
It sounds as though the throttle position sensor is playing up, or there is some problem with the Mass Airflow meter or even the lambda sensor.. but whatever it is, it will very likely have produced an error code and stored it in the ECU.