I celebrated too early. The backfire's still there. You can find one in each of the logs attached. In the first one, it's easy to find right after the WOT run at the end of the log. In the second one, it's somewhere in the first third. In any case, I am at a loss by now.

As you can see from the file names, I also changed the MAP sensor, just in case... to no avail. :(

Any more ideas? Anyone? Especially with her running so brilliantly the rest of the time, this issue is really bugging me...