Engine code says #1 cylinder is misfiring, I have changed plugs/wires and installed a new fuel filter. Any one have any more ideas as truck is great at highway speeds but chugs a little once started and going up through the gears. I have cleared the code for the service eng. lite and it keeps coming back once it chugs again. It always reads #1 Cylinder misfire. Could it be something in the ignition box ( where the plug wires go (coil pack??) not sure what it is called.

Thanks
Snakeyboy