2004 Mazda 6 3.0 weird misfire issue

I am having a cylinder 2, cylinder 4 and random misfire occurring on my 04 mazda6. I have changed spark plugs, ignition coils, injectors, vacuum lines, EGR valve/gasket, upper and lower intake gasket, smoke test, compression, O2 sensors, fuel damper.

Weird thing is the vehicle runs perfectly fine and gets great fuel mileage. You can’t feel the misfire and even notice there is one. check engine light does flash at higher speeds past 60mph. This case has puzzled me and a few other mechanics.