so my brother has a 4 runner with a 4.3 with tbi swapped in it. we just got it running and driving again. i test drove it and when i go to take off im barley on the gas and then all of a sudden for some reason it takes off on its own without me pressing the gas, but it only does it for a good 20 feet. has anyone had this problem before or know what might be causing this to happen?

 

I'm not completely familiar with the full functionality of throttle body injection so you may want to wait for someone that is to weigh in but my first suspects would be airflow meter and throttle position sensor. It may be a bad signal causing an excess of fuel to be released by the injector.

If you don't already have an appropriate FSM for that motor, I would pick one up/download one and hook up an ohm meter and test them, especially at low throttle.