code p0304

2002 windstar 3.8l. I have combed through all these forums trying everything listed and would apreciate some guidance. I was getting code p0401 for the longest time, i replaced the egr valve but it didnt change the code, so i figured it was the sensor. just recently the check engine light started blinking and the van was missing. First thing I did was change spark plugs and wires, no help. I then took apart the intake manifold and cleaned the egr ports which were dirty but not completely clogged, no change. I switched out #4 and 5 fuel injectors, no change. just today i switched the 4 and 5 wires at the coil and got p0304 and p0305. any thoughts on what i do know would be appreciated.

It seems that the newer windstars have issues with the coil pack not lasting as long.
As you have changed the injectors for the reported cylinders, replaced the spark plugs and wires, you might try replacing the coil pack.
The common failure with the coil pack is a crack in the epoxy case...and it arcs through the crack to ground, etc.
For this reason, it could ohm out correctly, but still be arcing.

Another thing you might try is a can of Berryman's B-12 Chemtool in the gasoline tank.
This will clean up the injectors.

i was getting P301 on my 2002 change plugs and wires same thing check coil pack tested good but replace it anyway and code clear and runs smooth now ,coil pack seems to break down on these model,