I have a 87 F150 with 302 and automatic trans. After I drive a distance, say 10 miles, at 55 or so and then come to a stop, when I press the pedal to go again the truck doesn't immediately respond. If I press it slightly again it takes off like crazy. I have new plugs, wires, rotor, egr valve. Does this condition relate to anything already done or something obvious that should be done?