Hello,new to the forum. Still haven't figured it all out yet, but trying. Have a problem with my 04 ram 5.7 it runs fin till you put your foot in it. Then it cuts out an throws a po300 code( multiple misfire).done a tune up, plugs,wires,egr,pcv cks. Still no change. Fuel pressure is 60 but will drop to about 50 when you gas it. Dies on cold starts, sometimes driving down the road. Was getting po335,po315 codes at first but not after tune up,just the po300 now. Thought it mite be a coil fail but not sure. What's a good way to check them? Any help would be appreciated.

 

THE WRONG PLUGS WILL CAUSE A P0300 CODE. USE COPPER CORE ONLY. sorry for yelling.

 

I used champion platinum that's what my buddy runs in his,with no prob. Should I change them?