P0304 misfire

[road_rascal]

Every once in awhile after running the van 30 mins or more, shutting it down, then firing it back up it sputters and bucks and acts like its vapor-locking. It will settle down after 10-15 seconds and run fine. Yesterday it did the same thing after a one hour highway run and finally triggered a CEL P0304 (misfire #4). When I did the isolator bolt procedure, I cleaned up the EGR ports (even though they weren't that bad). The van has 74K, plugs replaced at 52K and DPFE replaced at 50K. I have a hard time believing the coil has gone bad along with the wires. Would it be possible that a bad tank of fuel could have caused this? I put a double dose of cleaner in (MMO- I use it all the time- bikes and cars) and filled up at a different station. The CEL cleared on its own after 3 restarts and hasn't come back on, and the van is running great .