Dodge

Cylinder 4 misfire
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????