Ok so I am in way over my head, I dunno a damn thing about the 3.0L conversion/hybrid stuff. But I do have a 75mm maf and had problems with it. I had the same codes you had twice. They just don't seem to be able to get the calibration right. Take the pro-m off and put the stock one on. Let the computer reset and learn again. See if you are still running lean or rich. I agree with you, I don't think the maf is correct. Just trouble shoot, I am willing to bet the maf is the problem.
