Dodge

I have a 2008 Dodge Magnum 2.7 VIN T 24 valve.i bought the car and the only code was cylinder 4 misfire p0304 but it only misfired on cold start once it warmed up to operating temperature it smoothes out and idles excellent and drives excellent slow or fast.we replaced all coils, spark plugs (correctly gapped)and injectors yet still every morning same problem I was told it was the head gasket leaking coolant into cylinder 4 over night which is why cold start it was misfiring on that cylinder and ran fine after it burned up all the coolant in the cylinder itself which made sense to me so I replace the head gasket which did in fact need replaced also had a head bolt broke off into engine block so I replaced the engine had the heads resurfaced, pressure tested, honed out all 6 cylinders put new head gasket ,cleaned pistons, new pistons rings ,new head bolts, new timing chain kit, new engine mounts, new cam and crank sensors and much much more.still I put it all back together and still get cylinder 4 misfire but only on cold start after it warms it is done misfiring. anyone think they know what could be the cause????

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