Help! Ford Taurus Problem!?

While driving, under a more harder or light acceleration, the car seems to buck/hesitate, and can be light or get worse. While under extreme acceleration, I help the throttle steady while it was doing this, and the car gained more power as the bucking went away. Thats a correlation. Already ran fuel injector cleaner, and there is no cel on. Any ideas? (BTW, spark plugs look new, etc. Just bought car).