Im having this same exact problem. i dont know what it is either. im beginning to think its a sensor problem other than MAF and 02. TPS is a possibility and i was thinking possibly a faulty / intermittent cam sensor. you've never experienced a no start issue with it and then 20 mins later itll start right up?
not trying to jack your thread. but id like to help you out as well as have your help. More input the better.