When I take off from a dead stop the motor stumbles or hesitates. It dosen't do it all of the time, but, most of the time. Seems like it takes it second to get going. I have changed plugs, wires, fuel filter, and used fuel injector cleaner. No luck. When I have under a quarter of a tank it does it less. I'm stumped.

 

It's most likely the IAC (Idle air control) valve. Im having the same problem with my 4.6L...but Im not ready to lay down $60 for the valve yet..