Old thread here, but I thought I would update on my progress (oh god, I sure hope it's progress!).
The Baro pressure sensor and the MAP sensor are NOT THE SAME part number. Despite multiple websites showing them as interchangeable, and appearing cosmetically identical. A lot of websites don't even have a part for the BARO sensor, they just say the MAP is the same thing. The MAP is GM part 19418808, and the BARO sensor is 19418810. I do not know the difference. I can't find a difference. But I finally spent the big money ($50) on a genuine GM 19418810 from rock auto, and the code has disappeared. (for reference, generic MAP sensors are available anywhere for about $10).
Previously, I had disabled the CEL on HP tuners for the 2229 code, but I left the code active (just no light). The last several times I checked codes, it was gone. I have just now re-enabled the light, and we'll see if it comes back. I doubt it will, as the code was never totally disabled, but we'll see if anything changes by re-enabling the light.