Ok, I ordered a new O ring for the throttle body. When I removed the throttle body, the old O ring was still seated nicely in its groove, but it did seem a little thinner than the one I replaced it with. I switched back to the original v6 throttle body, and went back to the v6 MAF housing as well. I also added an auxiliary ground cable from the trans bell housing to the battery. I performed the throttle reset procedure and cleared the codes. After 1 quick test drive all seems ok. But it will have to drive fine for at least a week before I even begin to think the problem is solved.... I will update as time goes on.