I'm having a random / multiple cylinder misfire (p0300) at 5500 to 6,000 RPM in fourth gear or approximately 120 mph it used to do it the same thing in second and third at the same RPMs but after throwing spark plugs coils new filters it stopped and now only does it when cold and not attempt or topping out 4th and 5th gear I've tried a million and a half things and I'm really hoping that it's not cats my next course of action is fuel pressure test but I want to know what's wrong and I have no idea and no other form I've looked on can tell me.