P0304 misfire

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 :screwy: .