Last month I finished my EJ22E swap in my 1999 Legacy SUS. Ended up using a 1996 engine and did all recommended maint to it, brand new Y pipe, catalitic converters and knock sensor ( EJ25D part ) and a new ignition coil for the '96. I actually used the EJ25D harness and swapped the coil connectors.. It missfires warm now. 190* or so it will start and by 199-200* right before the fans kick on it's really rough. I remember that the EJ25D would have a more solid idle but it would miss at least 2 cylinders when warm, so I think this is related but back then, I thought it was due to the amount of coolant coming out the tail pipe due to the head gaskets.
Could the ignitor be the issue? where is it located. My last test run, I saw some light smoke coming from the driver side tire well while running about the same time it started missfiring, and it seemed to originate from the radiator area. I'm kinda hoping that smoke is what the problem is, and it's something like a failing ignitior. I have not run it since it started smoking tho, and it cleared up right when it was shut down... Any ideas?