backfire and acceleration problem

[lawdawg131]

My 2005 powerstroke occassionally will not want to accelerate from a stop, it moves forward at an idle even with the accelerater pushed to the floor and then will all of a sudden kick in. It will also backfire occassionally after driving at a constant cruising speed of lets say 45 as soon as you let off of the accelerator. I have changed both the fuel and air filters, with no change. Any help would help thanks.