Marauder is missfiring and stumbling

[MMG1989]

the codes 306 and 312 came up when my check engine light came on and im having stumbling problems and misfiring i changed my coils and my spark plugs but its saying that cylinder 6 is getting a misfire and i can hear my car puffing out of the pipes when it is just sitting still but it has a bad idle and is missing horribly and suggestions :mad::confused:

[Merrill]

Did you inspect / change the rubber boots between the coil and plug?
It is possible for the spark to jump through a bad spot and ground in
the valve cover not firing the plug.

[danrbarden]

Move, swap #6 coil and its boot to another cylinder position, see if the problem moves with the change. If not, look at the electrical connector for the coil, is it secure. Check for voltage at the number 6 coil. Hope this helps.
Danny