Hard to say what it is but my best suggestion to you to narrow it down is get a hold of an OBD-II scanner (buy one or borrow) and plug it in and keep it plugged in, go on freeway and force it to miss and when it does miss immediately read for any codes (even if there isn't a CEL on) sometimes the issue is so rare the PCM doesn't log it as continuous malfunction and won't turn on a CEL but it will register it as a pending code which the scanner can pick up and read even though as I said CEL isn't on. If it doesn't pull any pending codes you can eleminate 99% of the sensors leaving you with the possiblity of it being either a mechanical issue (bad fuel sending unit or sticking throttle body) or a weak ignition coil, if it does register a code well then it's self explanatory from there.
