You're hitting the gas too hard, slamming on the gas after a stop doesn't help the car go any faster- it makes the car sit and pause for a couple seconds. Gently, but quickly, push down the throttle evenly.
Remember, this isn't
a race car. I have an auto too. The same thing happened with my Lexus ES300 automatic. Also, you might want to have your throttle cable tightened. That could be why your accel isn't as firm. I also found while driving, when you get your revs up to 6 or the tach starts slowing down while accelerating, let go of the gas for a second and then accelerate again. You get a boost of power and I don't know why, it just works. Its like helping the car go.