While driving my 2003 4.0 fx4 super ranger i have a issue. If im agressive on the throttle (i.e. acceleration) or kick in to pass someone going slower than the speed limit, the truck runs as it might be flooded on gas.If i come to a stop after the acceleration or passing the truck drops rpms like it is about to stall. what could it be?

The truck is a auto. changed fuel filter three months ago along with plugs and cables.