I have the p0301 p0303 mystery code

[markandkilo]

Im new here so thanks in advance for any and all help
I have a 1998 2.5l manual Ranger the codes I get are p0303 and along with the codes come the misfire and really rough idle.
Heres what I have done
fuel filter
wires
plugs and they're platinum so im thinking of going back and putting in motorcraft
both coil packs
the injector in 1
checked and cleaned both maf and egr
fuel pressure test
compression test and it also help pressure for at least 20 minutes on 1 & 3
I also changed another sensor but I forget the name I think it was dpfe
Dont know what to do next Ive searched the net and all Ive done seems to be as far as anyone else has gone.
Any help or suggestions would be greatly appreciated

 

[97rangerxlt23]

i had a similar problem a year and a half ago.... swapped injectors around changed everything up top and nothing still ran rough and crappy....i had the P0303 code and come to find out i pulled the head and the exhaust valves on number 1,3,and 4 were cracked... and also the seats were sunk on the head and had to send her in...my machinest told me the material they use in the dual plug head are alittle softer than the others hence the sinking seats and probably the spider cracking on the valves...Hopefully its not as bad as yours but it was a nightmare to me racking my brain for over a week.... good luck man