Well... when you get on it, does the car hesitate? If you run it hard and the it doesn't hesitate, that means teh fuel pump is efficiently getting enough fuel to the car. I wonder if maybe you just have a carbon build up and the car needs a fuel enjection cleaning?

Did you just recently do an oil change?
Also it maybe the Idle air control valve, I know alot of times when cars have trouble idling it's because the Iacv is acting up. Any check engine lights?