I know exactly what your talking about! I’ve been having the same problem and have heard every thing you have said and more. Could be water in gas, TPS sensor, and a couple of other things. The problem for me arose when the car was driven hard, in the upper rpm's for a period of time.....autocross, mountain road ect.... Once the car was driven normally so to speak it wouldn’t be as noticeable but still there. Recently i installed some Borla headers on the car and when i reset the ECU the problem went away for the time being. I also notice that the air condition has an effect on the problem also.
P.S. the problem arose at about 36k