Ive got the po300 misfire code. Ive changed the plugs. coils look brand new. assuming they have been changed by the other owner. also moved them around and unplugged one at a time with no change. Runs rough as soon as you cut it on and smooths out after a few minutes. its at the point where the CEL is NOT on anymore but my code reader still picks up the code. sometimes it doesn't pick up a code at all but comes back before the computer is at readiness. sometimes the code wont clear at all. Not sure what to do anymore. Anyone had this happen to them 08 nitro btw