I responded to Mike privately, but here are a few more thoughts.

I think this may be the beginnings of a bad IMG. But...I am not 100% sure on that. The codes thrown are not for bad O2 sensors, they just indicate low voltage (a response to the lean condition IIRC). The other code P1171, indicates a lean condition in the fuel system under acceleration. I am not sure how the computer decides this. It should be through the 02 sensors, but...???

I guess it could be the fuel pump. The spec in my Chiltons indicates 41-46 as the fuel pressure. 38psi is not that far off and I cannot imagine it being the cause of the lean condition.

Other suggestions in the past have been to clean the MAF. I would suggest doing this. I would also consider pulling off the EGR valve and cleaning it too. If for some reason it is sticking, maybe it is causing a vacuum leak. Again, that is just a wild ass guess.

Good Luck,
Michael