we are actually doing the process of elimination. even if you bring it to the dealer, they'll do the same thing or worse recommend the wrong solution as a easy way out. parts that I think may cause a misfire are: fuel injector, head gasket leak, spark plug, ignition coil and maybe the wiring connector just needs cleaning. looks like he already eliminated the ignition coil by replacing it. next would be to swap the fuel injectors to different cylinder and see if the error code follows and if not, we can assume it's the head gasket and proceed from there such as taking it to the dealer to have the head gasket replaced. as he mentioned, the coolant level is still showing the same which I think is not the gasket. to the OP, keep us posted. I'm interested to find out.
OP - this has been going on for a year according to your first post... If you had spent the money to have the HG checked than I'd say keep tossing money at fuel injection related repairs. However, you keep spending money on everything but the $100 or so to find out for sure whether or not you have a serious issue. Hope in one hand and shit in the other, tell me which fills up first. Spend the money to have the issue checked, if it's not leaking, great. Figure out the cause of your issue however you or your mechanic sees fit but what sense does it make to spend money on something you have been chasing for over a year with no results. Obviously talking common sense to you have no effect as you refuse to listen to sound advice and it's your money so why bother asking us? As far as your question about your coolant level... your mechanic probably tops it off when you bring it in or it's not leaking bad enough yet to see a measurable loss in the overflow container. I'm sure it doesn't take much to make a motor stumble on a cold start for 10 seconds or so.
These are quotes from your first post:
"I am trying to convince myself it is not a head gasket " Obviously...
"Hate to have the dealer replace head gasket and that not be the problem" Why would you replace it without having it checked first? Because you refuse to listen?