THought 1: If it happened once and not since, forget it.
Thought 2: A car with those miles should have plugs and plug wires replaced. My Graphite was doing odd stuff around 100,000 miles that didn't add up I put 12 plugs and wires in it (ordered from Rob at Needswings, not Autozone crap) and everything cleared up right away. "
Thought 2A: Do not waste time "diagnosing" a car that has not had regular maintenance done. Original plugs and wires at almost 100,000 are at/beyond their service life.
Thought 2B: I'd not replace coils right now. Im not of the mindset that coils go bad nearly as often or as soon as plugs and wires, but coils are something to keep in mind as you go thru this.
THought 3: You never clearly answered the question of how old your air filters are. While at it, keep in mind the seal at the MAF intake and airbox is known to get 'loosy-goosy", this break of the seal changes the volume of air/vacuum drawn by the engine. This also means that one MUST secure the airbox in place properly and completely, this has come up before on here.
Thought 4: Vacuum leak? To check for a leak, warm engine by driving the car for 1/2 hour or more. PLace in Park/neutral. Raise hood. Yank the oil cap off. If the engine does not change it's idle at all, you have a pretty bad leak. If the engine speeds and slows, shakes and kinda freaks out, you have no real vacuum leak to speak of. You see, yanking the cap off creates an instant, severe vacuum leak and the engine should freak out due to this. If it does not, there is already a vacuum leak or horrible intake problem.

You might grab a code reader and see if there are any codes or pending codes and post them here for us. All we need are codes in the format: P0xxx where the x's are numbers 0-9.