couple of things i can think of, one the idle air control motor on the back of the throttle could be dirty which makes it hard for the pintle on it to move back and forth to let air in when you change gears or put a load on the engine while idling, cleaning it with some carb cleaner usually works. Another thing that i have had recent trouble with is my intake air temp. sensor. maybe try these
no check engine light i take it?
no check engine light i take it?